Also includes other refactoring.

Resolve "Fill pipeline source for external pipelines"

Closes #51651

See merge request gitlab-org/gitlab-ce!21814

Check frozen string in style builds

See merge request gitlab-org/gitlab-ce!21999

This also adds specs for 3 distinct situations:

2. When there is an unknown pipeline with just a build
3. When there is an unknown pipeline with no statuses
1. When there is an unknown pipeline with a build and a status

Docs: improve Pages overview (to deprecate feature page)

Closes #50507

See merge request gitlab-org/gitlab-ce!21798

[Docs] Document how to merge translations from Crowdin

See merge request gitlab-org/gitlab-ce!21924

Docs for Project/Groups members API with inherited members

Closes #51404

See merge request gitlab-org/gitlab-ce!21984

Add mysql_compatible_index_length to migration helpers

Closes #50253

See merge request gitlab-org/gitlab-ce!21852

Fix job_details.json schema

Closes #51927

See merge request gitlab-org/gitlab-ce!21983

closes https://gitlab.com/gitlab-org/gitlab-ce/issues/51927

Clarify subgroup permissions

See merge request gitlab-org/gitlab-ce!21769

Expains the differences between `api/projects/:id/members` and
`api/projects/:id/members/all` related to inherited members.

Documentation: Fix broken link of feature proposal template in issue_workflow.md

See merge request gitlab-org/gitlab-ce!21894

Fix karma out-of-memory failures

See merge request gitlab-org/gitlab-ce!21912

Rename block scope local variable in table pagination spec

See merge request gitlab-org/gitlab-ce!21969

Change class .label to .badge for 2FA label in group members view

See merge request gitlab-org/gitlab-ce!21759

Docs: improve Issue Boards overview (to deprecate feature page)

Closes #50503

See merge request gitlab-org/gitlab-ce!21905

Resolve "Geo: Does not mark repositories as missing on primary due to stale cache"

Closes #50211 and #44044

See merge request gitlab-org/gitlab-ce!21789

I attempted to refactor so that the caller of `wrap_method` passes in a
block, rather than a method name, but I was unsuccessful.

I kept getting the following error:

NoMethodError:
        undefined method `cache_method_output' for Repository:Class

If you can figure this out, then feel free to dry up these class methods
again without doing a send-within-a-send.

* Only truthy values are cached in Redis.
* All values are cached in RequestStore and in an instance variable.

And reuse `Gitlab::Utils::StrongMemoize`.

There is a subtle behavior change required to reuse StrongMemoize in
this case. The early fallback check now occurs *before* reading the
memoized value instead of after.

I think this is fine since a memoized value should only exist if
`exists?` is also already memoized as `true`.

Extend reports to support security features

See merge request gitlab-org/gitlab-ce!21892

Fix blue, orange, and red colors

See merge request gitlab-org/gitlab-ce!21972

Fix a sanity framework test

See merge request gitlab-org/gitlab-ce!21956

Add right margin to board-card-number

See merge request gitlab-org/gitlab-ce!21939

Adds an extra width to the responsive tables

See merge request gitlab-org/gitlab-ce!21928