... as otherwise they do not monitor the resource use within the test
files - until they are unity built.

Syncing behavior with `./configure`.

Closes #15003

Closes #15004

Add `CURL_CA_SEARCH_SAFE` build-time option to enable CA bundle search
in the `curl` tool directory. The lookup method was already used to find
`.curlrc` and `_curlrc` (on Windows). On Windows it overrides the unsafe
default `SearchPath()` method.

Enable with:
- cmake: `-DCURL_CA_SEARCH_SAFE=ON`
- autotools: `--enable-ca-search-safe`
- raw: `CPPFLAGS=-DCURL_CA_SEARCH_SAFE`

On Windows, before this patch the whole `PATH` was searched for
a CA bundle. `PATH` may contain unwanted or world-writable locations,
including the current directory. Searching them all is convenient to
pick up any CA bundle, but not secure.

The Muldersoft curl distro implements such CA search via a custom
patch for Windows:
https://github.com/lordmulder/cURL-build-win32/blob/cd652d4792c177c98b08b4309d3cac2b8dbbf9b0/patch/curl_tool_doswin.diff#L50

MSYS2/mingw-w64 distro has also been rolling a patch solving this:
https://github.com/msys2/MINGW-packages/blob/master/mingw-w64-curl/0001-Make-cURL-relocatable.patch
https://github.com/msys2/MINGW-packages/blob/master/mingw-w64-curl/pathtools.c

Also add option to fully disable Windows CA search:
- cmake: `-DCURL_DISABLE_CA_SEARCH=ON`
- autotools: `--disable-ca-search`
- raw: `CPPFLAGS=-DCURL_DISABLE_CA_SEARCH`.

Both options are considered EXPERIMENTAL, with possible incompatible
changes or even (partial) removal in the future, depending on feedback.

An alternative, secure option is to embed the CA bundle into the binary.

Safe search can be extended to other platforms if necessary or useful,
by using `_NSGetExecutablePath()` (macOS),
`/proc/self/exe` (Linux/Cygwin), or `argv[0]`.

Closes #14582

Closes #15002

Follow-up to 1b844967 #14992

- linux: bump up test parallelism for valgrind tests to `-j4`
  (from `-j2`). (EXPERIMENTAL)
- linux: drop `apt-get update` for the default architecture on the GHA
  native runner. It makes prereq install steps complete faster.
  The runner image gets weekly updates, and that should be enough to
  guarantee fresh packages in most cases:
  https://github.com/actions/runner-images/commits/main/images/ubuntu/Ubuntu2204-Readme.md
- aws-lc: use ninja with cmake.
- aws-lc: build examples with cmake.
- aws-lc: drop `apt update`.
- aws-lc, wolfssl, linux32, http3-linux: move building examples to
  the last step.
  Follow-up to 45202cbb #14906
- windows: formatting.

Closes #14992

They are still slow in these jobs/combinations.

- non-native/FreeBSD/arm64 autotools +36s
- non-native/FreeBSD/arm64 cmake +1m
- windows/linux-cross-mingw-w64 autotools +33s

These ones remain:
- linux/aws-lc cmake +6s
- windows/linux-cross-mingw-w64 cmake +12s

Follow-up to 71cf0d1f #14772

Add support for single-block binaries that contain all libtests and
unit tests respectively.

Enable with:
- autotools: `--enable-test-bundles`
- cmake: `-DCURL_TEST_BUNDLES=ON`

(They are compatible with `--enable-unity` and `-DCMAKE_UNITY_BUILD=ON`
options, for further speed-up.)

Makes libtests and unit tests build _fast_, needing little disk space
even in static mode. Similar to CMake unity mode, but with a custom
script, also supporting autotools builds.

The price is having to deal with symbols/macros colliding between
`lib*.c` and `unit*.c` sources. Maybe with naming conventions or other
solutions this can be improved gradually and reduce the need for manual
intervention by `mk-bundle.mk`. I've included a script that does the bulk
of detecting name collisions.

Also:
- CI: enable test bundles.
- CI: build tests in more jobs.
- lib2305: fix FILE handle leak.
- unit1661: fix memleak found by torture test by releasing the `bufref`
  structure in `unit_stop()` that was allocated in `unit_setup()`.
  ```
  test 1661...[bufref unit tests]
  Leak detected: memory still allocated: 13 bytes
   allocated by /home/runner/work/curl/curl/tests/unit/unit1661.c:70
   1661: torture FAILED: function number 1 in test.
  ```
  Ref: https://github.com/curl/curl/actions/runs/10967279334/job/30456745290?pr=14772#step:8:41

Similar test suite builds with autotools default and cmake+bundle+unity:
- GHA/Linux: 33s vs 7s
  https://github.com/curl/curl/actions/runs/10705668823/job/29681617374
- GHA/macOS 34s vs 2s
  https://github.com/curl/curl/actions/runs/10705668813/job/29681632885
- GHA/FreeBSD: 15m25 vs 6m21 (full workflow time, ~qemu)
  https://github.com/curl/curl/actions/runs/10705668811/job/29681607915
- GHA/Cygwin: 9m52 vs 32s
  https://github.com/curl/curl/actions/runs/10705668809/job/29681609965
- GHA/MSYS2: 3m52 vs 14s
  https://github.com/curl/curl/actions/runs/10705668808/job/29681624295
- GHA/mingw-w64: 5m45 vs 30s
  https://github.com/curl/curl/actions/runs/10705668808/job/29681628787

Autotools test suite builds compared between master -> `--enable-test-bundles`:
- GHA/Linux: 33s -> 9s (run tests: 22m23 -> 20m44)
  https://github.com/curl/curl/actions/runs/10710030193/job/29695932185
  https://github.com/curl/curl/actions/runs/10967831456/job/30458220344
- GHA/macOS: 25s -> 4s (run tests: 2m58 -> 2m24)
  https://github.com/curl/curl/actions/runs/10710030195/job/29695938444
  https://github.com/curl/curl/actions/runs/10967831452/job/30458225762
- GHA/non-native (FreeBSD): 4m8 -> 3m12 (full workflow time, ~qemu)
  https://github.com/curl/curl/actions/runs/10710030198/job/29695928401
  https://github.com/curl/curl/actions/runs/10967831458/job/30458212692
- GHA/Cygwin: 9m25 -> 1m9 (run tests: 9m19 -> 3m28)
  https://github.com/curl/curl/actions/runs/10710030212/job/29695928213
  https://github.com/curl/curl/actions/runs/10967831453/job/30458213268
- GHA/MSYS2: 3m54 -> 32s (run tests: 6m3 -> 3m59)
  https://github.com/curl/curl/actions/runs/10710030190/job/29704850591
  https://github.com/curl/curl/actions/runs/10967831449/job/30459280005
- GHA/mingw-w64: 5m42 -> 1m5 (run tests: 7m41 -> 5m36)
  https://github.com/curl/curl/actions/runs/10710030190/job/29704852058
  https://github.com/curl/curl/actions/runs/10967831449/job/30459280862
- Azure MSYS2 mingw64 openssl: 38m55 -> 11m58
  https://dev.azure.com/daniel0244/curl/_build/results?buildId=25546&view=logs&j=b58b8c59-0f61-52e9-0f9e-fad562a1e77f&t=0f9230a7-3b10-53ca-9938-700ece377c5e
  https://dev.azure.com/daniel0244/curl/_build/results?buildId=25547&view=logs&jobId=39473db1-3945-55d5-deb5-c218fad88dce&j=b58b8c59-0f61-52e9-0f9e-fad562a1e77f&t=0f9230a7-3b10-53ca-9938-700ece377c5e
- Azure Ubuntu default: 2m15 -> 55s (all build)
  https://dev.azure.com/daniel0244/curl/_build/results?buildId=25546&view=logs&j=9d58b9ac-e1e6-53b6-f83a-1f9f1d912522&t=a6b38d83-e7cf-5a9b-c762-a178412717b7
  https://dev.azure.com/daniel0244/curl/_build/results?buildId=25547&view=logs&jobId=39473db1-3945-55d5-deb5-c218fad88dce&j=9d58b9ac-e1e6-53b6-f83a-1f9f1d912522&t=a6b38d83-e7cf-5a9b-c762-a178412717b7

Cmake test suite builds compared between master -> `-DCURL_TEST_BUNDLES=ON` + unity:
- GHA/Linux: 29s -> 7s (run tests: 4m50 -> 4m57, 20m43 -> 20m45)
  https://github.com/curl/curl/actions/runs/10710030193/job/29695941814
  https://github.com/curl/curl/actions/runs/10705668823/job/29681622201
- GHA/Linux old: 44s -> 13s (bundle+no unity) (run tests: 5m5 -> 5m6)
  https://github.com/curl/curl/actions/runs/10718264094/job/29719794727
  https://github.com/curl/curl/actions/runs/10718653175/job/29721009613
- GHA/macOS: 32s -> 2s (run tests: 2m43 -> 2m40)
  https://github.com/curl/curl/actions/runs/10710030195/job/29695931956
  https://github.com/curl/curl/actions/runs/10705668813/job/29681638937
- GHA/non-native (*BSD): inconclusive (full workflow time, ~qemu)
  https://github.com/curl/curl/actions/runs/10710030198
  https://github.com/curl/curl/actions/runs/10705668811
- GHA/Cygwin: 3m9 -> 32s
  https://github.com/curl/curl/actions/runs/10710030212/job/29695929075
  https://github.com/curl/curl/actions/runs/10705668809/job/29681609965
- GHA/MSYS2: 2m24 -> 14s
  https://github.com/curl/curl/actions/runs/10710030190/job/29704850996
  https://github.com/curl/curl/actions/runs/10705668808/job/29681624295
- GHA/mingw-w64: 3m56 -> 30s (run tests: 4m2 -> 3m52)
  https://github.com/curl/curl/actions/runs/10710030190/job/29704852219
  https://github.com/curl/curl/actions/runs/10705668808/job/29681631393
- GHA/mingw-w64-old: 7m19 -> 1m44 (run tests: 3m30 -> 2m53)
  https://github.com/curl/curl/actions/runs/10710030190/job/29704849763
  https://github.com/curl/curl/actions/runs/10705668808/job/29681622329
- GHA/MSVC: 3m22 -> 13s (run tests: 9m43 -> 4m22)
  https://github.com/curl/curl/actions/runs/10710030190/job/29704850411
  https://github.com/curl/curl/actions/runs/10705668808/job/29681623313
- AppVeyor CI MSVC 2008: 4m3 -> 45s (full build)
- AppVeyor CI MSVC 2010: 2m56 -> 1m8 (full build)
- AppVeyor CI MSVC 2022: 10m19 -> 2m23 (full build)
  https://ci.appveyor.com/project/curlorg/curl/builds/50538455
  https://ci.appveyor.com/project/curlorg/curl/builds/50536558
- AppVeyor CI total build time: 10m30 (master) -> 6m48 (unity) -> 4m5 (bundle) -> 3m24 (bundle+unity) -> 5m7 (bundle+unity+all jobs building tests)

Closes #14772

- unroll two short loops.
- unfold lines.
- merge lines with their comments.
- add missing quotes.
- tidy up grammar in error/warning messages.

Cherry-picked from #14692
Closes #14998

Replace invalid C with `#error`.

Cherry-picked from #14692
Closes #14997

C89, Schannel, Secure Transport, contractions.

Cherry-picked from #14692
Closes #14996

Cherry-picked from #14692
Closes #14995

Before this patch, each build tool generated `tests/configurehelp.pm`
manually.

Ref: https://github.com/curl/curl/pull/14802#issuecomment-2332734326
Closes #14819

- autotools: add support for custom prefix.
  Usage: `--enable-versioned-symbols=MYPREFIX_`
  Catching up with cmake.

- add default versioned prefix for Rustls builds.

- delete `HIDDEN` entry from version script `lib/libcurl.vers.in`.
  It referred to symbol names that never existed in libcurl.

- cmake: use `lib/libcurl.vers.in` as a template instead of generating
  it from scratch. Adapt `./configure` accordingly, and add comments
  to keep hard-wired soname in sync with `lib/Makefile.soname`.

- autotools: delete Schannel and Secure Transport version prefixes.
  Windows and macOS don't support the versioned symbols option.

Follow-up to 7b144497 #14378
Closes #14818

Before this patch, only these triplets were considered Apple:
`<cpu>-apple-darwin`

After this patch, these are also considered Apple:
`<cpu>-apple-(ios*|tvos*|visionos*|watchos*|<ETC>)`

`$host_os` (the last third of the triplet) still has a valid use
to differentiate between OS flavours, though for now this isn't
used, aligning with CMake.

Closes #14728

Add CI checker to compare `libcurl.pc` and `curl-config` files
generated by autotools and cmake builds.

Fix differences and apply tiny cleanups:
- curl-config: use single-quotes for literals.
- curl-config: quote all variables.
- curl-config: replace double with single quotes in a substituted value
  that's always literal (`@prefix@`).
- libcurl.pc: spelling in `Description:`.
- libcurl.pc: avoid substitution in a comment.
- cmake: fill `libdir` with `${exec_prefix}` instead of a literal.
  To sync with './configure'.
- configure: fix `CURL_CA_BUNDLE` value to not generate nested quotes
  in `curl-config`.
- configure: add missing `LDFLAGS` to `Libs.private` in `libcurl.pc`.
  To sync with CMake.
- cmake: skip adding `CMAKE_C_IMPLICIT_LINK_LIBRARIES` for MINGW and
  UNIX. They added these values as seen in CI:
  MINGW: `-lmingw32 -lgcc -lmoldname -lmingwex -ladvapi32 -lshell32 -luser32 -lkernel32 -lmingw32 -lgcc -lmoldname -lmingwex`
  Linux: `-lgcc -lgcc_s -lc -lgcc -lgcc_s`
- cmake: delete FIXME about enabling libssh2 by default.
  `./configure` has special defaults for these packages (called: "off"):
  brotli, zstd, libpsl, libssh2, libssh, wolfssl, librtmp
  It looks for them, but only at system locations, which makes them
  never detected e.g. on macOS. CMake doesn't offer such default mode
  for now.
- GHA/macos: drop now redundant `-DCURL_DISABLE_LDAPS=ON`.
- cmake: use `CMAKE_INSTALL_INCLUDEDIR` and `CMAKE_INSTALL_LIBDIR`
  instead of hardcoded `include`/`lib` when generating `libcurl.pc`.

Updates to the GHA workflow:
- move autotools out-of-tree and rename cmake out-of-tree directory
  to `bld_cm` to tell it's cmake.
- disable static libcurl for `./configure` to match cmake.
- enable `pkg-config` debug output with `./configure`.
- dump list of Homebrew packages on macOS.
- dump `./configure` detailed logs.
- disable zstd and brotli for Linux, to match cmake.

There remain differences, mostly due to detection order and method. Also
some values are inherently different when using CMake and autotools,
such as `--cc`, `--configure`. autotools also generates duplicates for
`-lssl` and `-lcrypto`. macOS LDAP wants to link `-lber` while autotools
doesn't. Some build defaults are also different in autotools and cmake.
These differences are smoothened out for now by the checker script, or
via build options. Notice that lib order (a dupes) _can_ be significant
in some cases. E.g. the binutils linker is infamous for that on Windows.

Closes #14681

- CPPFLAGS: `-DCURL_DISABLE_IPFS`
- configure: `--disable-ipfs`
- cmake: `-DCURL_DISABLE_IPFS=ON`

Fixes #14824
Closes #14827

- delete redundant Schannel check.

- move `feature_ssl` check one level up from `FindWin32CACert()`.

- check `feature_ssl` early to skip a bunch of CA bundle search logic
  for no-ssl configurations.

Reviewed-by: Jay Satiro
Closes #14841

Try to enable as much as possible to check for compatibility with old
dependencies.

Follow-up to 3efba94f #14765

Unity mode seems to defeat the scanner and miss issues.

before, miss: https://github.com/curl/curl/actions/runs/10967056702/job/30456136390
after, OK: https://github.com/curl/curl/actions/runs/10967128744/job/30456330732#step:35:1232

Tested with PR commit:
https://github.com/curl/curl/pull/14880/commits/32854bb30861e757d4f8d61d303c1b1f0e55bd26

Follow-up to 60c3d044 #14815
Closes #14987

- make `curl.1` and `curl.txt` depend on `DPAGES`.
  To trigger a rebuild when an individual manpage is updated.

- tell CMake that the cmdline-opts command also creates `curl.txt`.

- make `tool_hugehelp.c` depend on `curl.txt` (was: `curl.1`), to match
  what it actually uses for input.

- stop using `generate-curl.1` as an indirect way to create `curl.txt`
  in time for `tool_hugehelp.c`. After the fixes above there is a direct
  depedency chain between them.

- move `ASCIIPAGE` and `MANPAGE` variables to top-level, re-use them in
  `src` and prefix them with `CURL_` to avoid clashing with other
  projects.

- drop double quotes from `generate-curl.1` as a hint that it is not
  a filename, but a target name.

- src: tidy up order of dependency lists.

Closes #14883

Suppress deprecation warnings the closest to the deprecated code, using
`CURL_IGNORE_DEPRECATION()`. Then drop build-specific suppressions, and
file-wide ones. The latter is not compatible with Unity mode. Also
replace manual suppressions with a macro to apply to all compilers with
deprecation warning support. Also enable deprecation warnings for clang.

- curl/curl.h: enable deprecation warnings for clang.

- docs/examples: stop setting `CURL_DISABLE_DEPRECATION` with autotools.
  Suppression moved to C-level earlier. Syncs with cmake.
  Follow-up to 5fc61a37 #14123

- tests/http/clients: stop setting `CURL_DISABLE_DEPRECATION` in
  autotools. If it becomes necessary in the future, it can be done in
  C via the macro. Syncs with cmake.

- lib1545: stop setting `CURL_DISABLE_DEPRECATION` in autotools.
  Drop guard from test source.
  Follow-up to 0f103600 #12444

- libtest, unit: replace `CURL_DISABLE_DEPRECATION` with
  `CURL_IGNORE_DEPRECATION()`.

- docs/examples: replace pragmas with `CURL_IGNORE_DEPRECATION()`.

Closes #14789

Enable `CURL_USE_PKGCONFIG` by default for more environments:

- for `MINGW` targets when not using cross-compilation.
- stop restricting vcpkg to MSVC. (this currently unlocks mingw,
  also unlocked by the update above.)

Also:
- cache `CURL_USE_PKGCONFIG` in `CURLConfig.cmake`.
  Suggested-by: Kai Pastor

Follow-up to c555ab46 #14575
Closes #14658

- use cmake with ninja.
- drop unnecessary packages.

Also:
- Linux: switch to Ubuntu 20.24 runner. Initially for newer packages,
  then left it there for variation and as canary.
- Linux: make it easier to enable valgrind by dropping `-n` tflags.
- Linux: show `curl -V` after build.
- Linux: sync job names with macOS.
- Linux, macOS: review and adjust job timeouts.
- Linux, macOS: sync job configs more:
  Linux: enable libssh2, macOS: enable brotli, zstd, libssh2.
- macOS: prefer `source` (over manual `PATH` editing) for `venv` setup.
- macOS: drop redundant `-DENABLE_CURLDEBUG=ON`.
- macOS: drop redundant `-n` tflags. There is no valgrind on macOS.
- macOS: allow overriding test parallelism per job.
- macOS: unlock all disabled tests for torture jobs.

Speed-ups (configure/build stage):
- Linux !FTP: 83s -> 36s
  before: https://github.com/curl/curl/actions/runs/10948030198/job/30398134647
  after: https://github.com/curl/curl/actions/runs/10961987675/job/30440179978?pr=14972
- Linux FTP: 79s -> 32s
  before: https://github.com/curl/curl/actions/runs/10948030198/job/30398137070
  after: https://github.com/curl/curl/actions/runs/10961987675/job/30440182406?pr=14972
- macOS !FTP: 98s -> 29s
  before: https://github.com/curl/curl/actions/runs/10960141275/job/30434081412?pr=14972
  after: https://github.com/curl/curl/actions/runs/10960141275/job/30434082357?pr=14972
- macOS FTP: 129s -> 29s
  before: https://github.com/curl/curl/actions/runs/10960141275/job/30434082041?pr=14972
  after: https://github.com/curl/curl/actions/runs/10960141275/job/30434083050?pr=14972

Closes #14972

Implement the "unity" builds as known from CMake, but for autotools.
It's limited to `lib` and `src` (CMake also supports it in `tests`).

Enable with: `--enable-unity` (disabled by default)

Unity builds speed up builds significantly. Cygwin and Windows builds in
particular, but the effect is noticeable on most systems. It also allows
discovering unity issues with autotools, benefitting also CMake when
building the same combination. In CI it makes turnaround times quicker.

This closes build performance with CMake. autotools still lags behind
because it builds shared and static libcurl in two, separate passes.
CMake does it in one. Manpage compilation isn't batched, it is in CMake.
After unity and test bundle support the slowest parts of the build are
the configuration phase (which is effectively a tedious, non-parallel,
compilation and/or linking of 300+ tiny programs. The next bottleneck
is compiling individual examples and finally test servers (only slow
with autotools).

The autotools implementation is slightly less efficient than CMake,
because 3 sources are permanently excluded while in CMake this isn't
necessary and solved more efficiently while building libtests. There is
also no 'unity' support for tests, making them a less efficient also.

Enable it in CI for most `configure` jobs. Except in GHA/dist (though
it works fine there too), to use the default config there. Also skip for
the Linux AWC-LC job where it made builds time a few seconds longer
(reason undiscovered.)

Autotools test suite builds compared between master -> `--enable-unity`:
- GHA/Linux: 32s -> 12s
  https://github.com/curl/curl/actions/runs/10705668823/job/29681617374
  https://github.com/curl/curl/actions/runs/10742978889/job/29796766297
- GHA/macOS: 37s -> 10s
  https://github.com/curl/curl/actions/runs/10705668813/job/29681632885
  https://github.com/curl/curl/actions/runs/10742978699/job/29796768875
- GHA/FreeBSD: 15m25 -> 10m58 (full workflow time, ~qemu)
  https://github.com/curl/curl/actions/runs/10705668811/job/29681607915
  https://github.com/curl/curl/actions/runs/10742978937/job/29796766115
- GHA/Cygwin: 3m32 -> 1m21
  https://github.com/curl/curl/actions/runs/10705668809/job/29681609965
  https://github.com/curl/curl/actions/runs/10742978645/job/29796756933
- GHA/MSYS2: 2m42 -> 50s
  https://github.com/curl/curl/actions/runs/10705668808/job/29681621166
  https://github.com/curl/curl/actions/runs/10742978662/job/29799739289
- GHA/mingw-w64: 5m32 -> 1m23
  https://github.com/curl/curl/actions/runs/10705668808/job/29681628787
  https://github.com/curl/curl/actions/runs/10742978662/job/29799741568

Closes #14815

- Move `docs/examples` builds under a separate target.

- Make `BUILD_EXAMPLES` default to `ON`. It means to generate the rules
  for `docs/examples` by default, but not build them. To build them,
  an explicit `make curl-examples` (or ninja, etc) command is necessary.
  This syncs behaviour with autotools, and also how both cmake and
  autotools are building tests.

- GHA: update cmake jobs to use the new way of building examples.

- GHA: move examples build step at the end of the job, after building
  and running tests. This allows to have build and test run results
  faster, and leave the seldom-changing examples build to the end.
  Building examples is the slowest build step with no practical way to
  make them fast.

- appveyor: enable building examples in two old-MSVC jobs.

- examples: fix examples to build cleanly with old MSVC versions.

- GHA/non-native: move example build log under a GHA foldable section.

- GHA/windows: move building examples into separate step for Linux cross
  jobs.

Follow-up to dfdd978f #13491
Closes #14906

- show invocation arguments (tflags) in the log.
- show `curl -V` protocols in the log.

Closes #14985

When ending an FTP upload, we shut down the connection gracefully, since
the server should be notified we had send all bytes. Mostly, this is a
NOP without TLS involved. With TLS, close-notify messages should be
exchanged.

As reported in #14843, not all servers seem to do that. Since it is the
server's responsiblity to check it has received everything, we just log
the timeout and proceed as if everything is fine.

In the receive direction, we still fail the transfer if the server does
not shut down its direction properly.

Fixes #14843
Reported-by: Rasmus Melchior Jacobsen
Closes #14848

When a transfer is set for a speficif HTTP version, only lookup that
protocol in the alt-svc mappings. When no speicific version is
requested, scan all entries as before.

Closes #14966

- When searching for existing connections, interpret the
  default CURL_HTTP_VERSION_2TLS as "anything goes". This
  will allow us to reuse HTTP/3 connections better
- add 'http/1.1' as allowed protocol identifier in Alt-Svc
  files
- add test_02_0[345] for testing protocol selection on
  provided alt-svc files

Fixes #14890
Reported-by: MacKenzie
Closes #14966

Closes #14983

This prevents our torture tests from detecting and getting trapped by
memory leaks in libssh2.

Closes #14984

The implementation did not check the poll flags when a ssh_connect()
EAGAINed. Also the poll check did not allow for both directions
to be signalled by libssh, which it does.

This appeared during CI testing with higher paralellism.

Closes #14982

With higher parallelism in CI, the ASSERT triggered on pause tests.
Strengthen the check. We might want to think about removing
KEEP_RECV_PAUSE|KEEP_SEND_PAUSE altogether.

Closes #14981

"readline() on closed filehandle $val at valgrind.pm line 45."

Closes #14977

Move them from `install_steps` to `install_packages`.

Also:
- stop installing valgrind for the event-based job where valgrind is
  explicitly disabled with tflags `-n`.
- stop installing valgrind for the hyper job. It wasn't enabled (by
  accident) before, and when actually enabled, it fails to pass tests:
  ```
  TESTFAIL: These test cases failed: 11 25 28 30 36 37 43 45 69 78 88
    90 94 129 153 154 155 158 160 170 176 178 187 193 207 217 233 234
    243 257 262 276 287 302 309 317 318 330 376 379 388 394 395 398
    415 427 440 441 493 497 498 547 548 551 552 555 590 599 644 650
    1031 1067 1071 1079 1089 1090 1104 1127 1128 1141 1142 1168 1172
    1174 1197 1239 1244 1261 1297 1314 1412 1416 1424 1430 1431 1432
    1433 1434 1473 1479 1480 1511 1531 1909 2081 2306 3015 3102
  ```
  Ref: https://github.com/curl/curl/actions/runs/10957987291/job/30427294361?pr=14979#step:41:50381
  Hyper is also scheduled for removal in February 2025.

Closes #14979

Refs: #14927 #14932 #14971
Closes #14922