Fix concurrent fork network migrations

Closes #41487

See merge request gitlab-org/gitlab-ce!16988

Memoize MergeRequest#rebase_in_progress? to prevent N+1 queries in Gitaly

Closes gitlab-ee#4857

See merge request gitlab-org/gitlab-ce!16990

Move Namespace to Gitaly using OPT-OUT

See merge request gitlab-org/gitlab-ce!15910

MergeRequest#rebase_in_progress? and MergeRequest#rebase_path were called
twice each time per request. This memoization helps reduce the overall number
of queries.

See https://gitlab.com/gitlab-org/gitlab-ee/-/jobs/51616319 as a failing
job.

Closes gitlab-org/gitlab-ee#4857

Remove N + 1 block for Root#show

Closes #37434 and gitaly#996

See merge request gitlab-org/gitlab-ce!16968

Fix sample fstab file in GitLab HA docs

See merge request gitlab-org/gitlab-ce!16985

Update style_guide_scss.md

See merge request gitlab-org/gitlab-ce!16651

Since the migration might be queued already and be rescheduled when it
fails on a uniqueness error, this should help clearing the background
migration queue faster.

Since populating the fork networks was scheduled multiple times
because of bugs that needed to be fixed:

- https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/15595/
  Creating fork networks for projects that were missing the root of
  the fork network.

- https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/15709
  The API allowed creating forked_project_links without
  fork_network_members.

Scheduling this migration multiple times would case it to run
concurrently. Which in turn would try to insert the same data into
`fork_network_members` causing duplicate key errors.

This avoids running the migration multiple times.

Resolve "Expose GitLab license/plan as a CI/CD variable"

Closes #40994

See merge request gitlab-org/gitlab-ce!16936

Annotate charts page for internationalization

See merge request gitlab-org/gitlab-ce!16687

Resolve "New design for user deletion confirmation in admin area"

Closes #41301

See merge request gitlab-org/gitlab-ce!16811

Resolve "New design for cancel / stop pipeline confirmation"

Closes #41297

See merge request gitlab-org/gitlab-ce!16813

Annotate graph page for internationalization

See merge request gitlab-org/gitlab-ce!16688

Resolve "New design for project deletion confirmation"

Closes #41300

See merge request gitlab-org/gitlab-ce!16812

Fix tests

Address code review feedback

Fix tests

The nobootwait option is no longer a valid option in Ubuntu 16.04.
Use nofail instead:

https://askubuntu.com/questions/786928/ubuntu-16-04-fstab-fails-with-nobootwait

Use prometheus-client-mmap released, final version

See merge request gitlab-org/gitlab-ce!16984

Merge branch '42864-update-vendored-autodevops-yml-for-latest-browser-performance-testing-changes' into 'master'

Update vendored AutoDevOps YML for latest Browser Performance Testing changes

Closes #42864

See merge request gitlab-org/gitlab-ce!16982

Migrate Git::Blob.batch to Gitaly

Closes #37445 and gitaly#985

See merge request gitlab-org/gitlab-ce!16928

Add instructions for source installation to mysql_to_postgresql.md

See merge request gitlab-org/gitlab-ce!16983

Closes gitaly#985

Resolve "Cancelling a second comment edit doesn't return its state to before the edit"

Closes #42462

See merge request gitlab-org/gitlab-ce!16869

Replace $.ajax in profile.js with axios

See merge request gitlab-org/gitlab-ce!16895

Update prometheus gem to version 0.9.1.pre.rc.2 fixing segfaults happening on metrics deletion

See merge request gitlab-org/gitlab-ce!16964

Replace $.get in diff file editor with axios

See merge request gitlab-org/gitlab-ce!16896

Cache Gitaly FindCommit RPC response

See merge request gitlab-org/gitlab-ce!16949