updateref: Setup a cause of the failure

When Prepare() or Commit() method of the Updater was called inside
UpdaterWithHooks#UpdateReference method the errors returned were
thrown away. Because of it we were missing important part of the
failure cause - the output of the failed git operation. In order to
fix it we now return it as part of the Error instance. The call sites
inspects the error and logs it in case there is any metadata
associated with it.

Closes: https://gitlab.com/gitlab-org/gitaly/-/issues/4677
Changelog: added