Fix call stack size exceeded group milestone description autocomplete

Closes #39020

See merge request gitlab-org/gitlab-ce!14972

Merge branch 'pawel/bump_prometheus_gem_to_fix_read_all_values_returning_bad_data-39504' into 'master'

Update Prometheus Gem to fix problem caused by using wrong data offsets

See merge request gitlab-org/gitlab-ce!15081

Changed project select to use it independently and not onlt as a combobutton

See merge request gitlab-org/gitlab-ce!15043

Fix 500 error for old (somewhat) MRs

Closes #36540

See merge request gitlab-org/gitlab-ce!14945

Upgrade Gitaly to v0.50.0

See merge request gitlab-org/gitlab-ce!15050

Merge branch '39054-activerecord-statementinvalid-pg-querycanceled-error-canceling-statement-due-to-statement-timeout' into 'master'

Resolve "ActiveRecord::StatementInvalid: PG::QueryCanceled: ERROR:  canceling statement due to statement timeout"

Closes #39054

See merge request gitlab-org/gitlab-ce!15063

Add docs for backing up to Google Cloud Storage

See merge request gitlab-org/gitlab-ce!15074

Add missing circuitbreaker metrics to prometheus documentation

See merge request gitlab-org/gitlab-ce!15062

Ci::Build tag is a trait instead of an own factory

See merge request gitlab-org/gitlab-ce!15077

Fix widget of locked merge requests not being presented

See merge request gitlab-org/gitlab-ce!15069

Minor annoyance of mine, and there were a couple of things wrong, for
example:
1. Switching on a property is just a trait
2. It didn't inherrit from its parent

Find and replace through the code based fixed all occurances.

[CE backport] Saved configuration for issue board

See merge request gitlab-org/gitlab-ce!15009

Use the correct project visibility in system hooks

Closes #39496

See merge request gitlab-org/gitlab-ce!15065

grab the correct username when confirming secondary email

Closes #39366

See merge request gitlab-org/gitlab-ce!15010

Remove Autosave class from global namespace

See merge request gitlab-org/gitlab-ce!14856

Update docs on creating MRs

See merge request gitlab-org/gitlab-ce!14982

Fetch the merged branches at once.

Checking it one by one in the view. We don't cache this yet
because this would already much improve the performance.

A naive test against a particularly large repository:

``` ruby
begin
  now = Time.now
  branches.map{ |b| r.merged_to_root_ref?(b.name) }
  Time.now - now
end # 8.265830782
```

Around 10 times faster:

``` ruby
begin
  now = Time.now
  r.merged_branches(branches.map(&:name))
  Time.now - now
end # 0.807405397
```

This should make the branches page usable.

See merge request gitlab-org/gitlab-ce!14729

Move doc/development/ee_features.md to CE

See merge request gitlab-org/gitlab-ce!15066

Cache commits on the repository model

See merge request gitlab-org/gitlab-ce!14863

Avoid using Rugged in Gitlab::Git::Wiki#preview_slug

See merge request gitlab-org/gitlab-ce!15054

For MRs with many thousands of commits, `SELECT DISTINCT(sha)` will be very
slow.

What we can't do to fix this:

1. Add an index. Postgres won't use it for DISTINCT without a lot of ceremony.
2. Do the `uniq` in Ruby. That can still be very slow with hundreds of
   thousands of commits.
3. Use a subquery. We haven't removed the `st_commits` column yet, but we will
   soon.

Until 3 is available to us, we can just do 2, but also add a limit clause. There
is no ordering, so this may return different results, but our goal with these
MRs is just to get them to load, so it's not a huge deal.

Add configurable option to display username in user avatar link component

See merge request gitlab-org/gitlab-ce!14902

Sanitize k8s default_namespace

Closes #38692

See merge request gitlab-org/gitlab-ce!15053