On each read/write operation praefect requires to know which
gitaly node is a primary. For mutator operations it used to
define from what node the response will be returned back to
the client. For the read operations it is used to redirect request
to or as a fallback option for reads distribution in case it
is enabled. The default strategy for defining the primary is
'sql' which means the primary is tracked inside of the Postgres
database and praefect issues select statement into it each time
it needs to define the current primary. It creates a high load
on the database when there are too many read operations (the
outcome of the performance testing).

To resolve this problem we change the logic of retrieval of
the set of up to date storages to return all storages including
the primary. With it in place we don't need to know the current
primary and use any storage that has latest generation of the
repository to serve the requests. As this information is cached
by the in-memory cache praefect won't create a high load on the
database anymore.

This change also makes check IsLatestGeneration for the primary
node redundant as it won't be present in the set of consistent
storages if its generation not the latest one.

Fix linting issues

Closes: https://gitlab.com/gitlab-org/gitaly/-/issues/3337