This MR introduces tracking of the `rebase_jid` for merge requests. As
with `merge_ongoing?`, `rebase_in_progress?` will now return true if a
rebase is proceeding in sidekiq.

After one release, we should remove the Gitaly-based lookup of rebases.
It is much better to track this kind of thing via the database.

Make Housekeeping button do a full garbage collection

Closes #63349

See merge request gitlab-org/gitlab-ce!30289

Add released_at field to releases API
Add released_at column to releases table
Return releases to the API sorted by released_at

Previously the Housekeeping button and API would use the counter of last
pushes to determine whether to do a full garbage collection, or whether
to do one of the less comprehensive tasks: a full repack, incremental
pack, or ref pack. This was confusing behavior, since a project owner
might have to click the button dozens of times before a full GC would be
initiated.

This commit forces a full GC each time this is initiated. Note that the
`ExclusiveLease` in `HousekeepingService` prevents users from clicking
on the button more than once a day.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/63349

Tidy spec for API::ProjectClusters

See merge request gitlab-org/gitlab-ce!30154

[master] Fix MR head pipeline leak

See merge request gitlab/gitlabhq!3148

Fix type authorizations in GraphQL

See merge request gitlab/gitlabhq!3170

Expose merge requests count based on user access

See merge request gitlab/gitlabhq!3157