The various LDAP check Rake tasks have long supported a SANITIZE
environment variable. When present, identifiable information is
obscured such as user names and project/group names. Until now,
the LDAP check did not honor this. Now it will only say how many
users were found. This should at least give the indication that
the LDAP configuration found something, but will not leak what
it is. Resolves #56131

Upgrade Gitaly to v1.43.0

See merge request gitlab-org/gitlab-ce!28867

We've already migrated all the legacy artifacts to the new realm,
which is ci_job_artifacts table.
It's time to remove the old code base that is no longer used.

It used to be the case that GitLab created symlinks for each repository
to one copy of the Git hooks, so these ran when required. This changed
to set the hooks dynamically on Gitaly when invoking Git.

The side effect is that we didn't need all these symlinks anymore, which
Gitaly doesn't create anymore either. Now that means that the tests in
GitLab-Rails should test for it either.

Related: https://gitlab.com/gitlab-org/gitaly/issues/1392#note_175619926

Replaced Settings with Gitlab.config for uniformity

The previous code works fine when running specs, but the API
does not exist outside that environment.

This is a small polishing on the storage migration and storage rollback
rake tasks. By aborting a migration while a rollback is already
scheduled we want to prevent unexpected consequences.

# Conflicts:
#   spec/tasks/gitlab/backup_rake_spec.rb

Specs were reviewed and improved to better cover the current behavior.
There was some standardization done as well to facilitate the
implementation of the rollback functionality.

StorageMigratorWorker was extracted to HashedStorage namespace were
RollbackerWorker will live one as well.