Implement external validation during pipeline creation

Closes #34015

See merge request gitlab-org/gitlab!21134

Stubs out the major elements of the external validation pipeline chain
step.

Changes database engineer to just engineer

See merge request gitlab-org/gitlab!21774

Rectifies Database Query Comments guide to just use Engineer instead of
DB engineer, as we don't have those on call

Block empty params to MR target branch autocompletion

Closes #31830

See merge request gitlab-org/gitlab!21748

Show correct warning on issue when project is archived

See merge request gitlab-org/gitlab!20078

Fix assignee url issue in board sidebar

Closes #35842

See merge request gitlab-org/gitlab!20992

Add doc for blame and history UI functionality

Closes #39106

See merge request gitlab-org/gitlab!21609

While the functionality was created ~ 7 years ago, it was never doc'd

Resolve "Link Group name on group's Admin page"

See merge request gitlab-org/gitlab!21709

Merge branch '38056-change-the-clipboardtext-property-requirement-inside-the-panel_type-component' into 'master'

Change the `clipboardText` to optional in panel_type component

Closes #38056

See merge request gitlab-org/gitlab!21717

Remove var from app/assets/javascripts/commit/image_file.js

Closes #36266

See merge request gitlab-org/gitlab!21649

Upgrade @sentry/browser to 5.10.2

See merge request gitlab-org/gitlab!21702

Update static ip link

See merge request gitlab-org/gitlab!21770

Add child label to commit box (2/3)

See merge request gitlab-org/gitlab!21323

Refactor end-to-end test to make it more robust

Closes #36688

See merge request gitlab-org/gitlab!21652

And simpler.

Resolve "Replace fa-bullhorn with GitLab SVG bullhorn icon (all instances)"

Closes #41934

See merge request gitlab-org/gitlab!21587

Marginalia with feature check on app start

See merge request gitlab-org/gitlab!21364

Switch to DockerHub for Elasticsearch image

See merge request gitlab-org/gitlab!21750

Changelog entries for MRs 21524 and 21607

See merge request gitlab-org/gitlab!21768

Skip updating LFS objects in mirror updates if repository has not changed

Closes #38256

See merge request gitlab-org/gitlab!21744

We were being rate-limited by docker.elastic.co:

```
Unavailable: Back-end server is at capacity (executor_docker.go:188:0s)
elasticsearch : 5.6.12
```

[ci skip]

[ci skip]

UI improvements in the views for new project from template and the user groups and snippets

Closes #39469 and #39465

See merge request gitlab-org/gitlab!21524

Permissions for vulnerabilities

See merge request gitlab-org/gitlab!21265

Sort Sentry error list by first seen, last seen or frequency

See merge request gitlab-org/gitlab!21250

Added sort control, remove View in Sentry, updated tests

Add example of .gitlab-ci.yml that uses only: [merge_requests] and excludes specific branches

Closes #33573

See merge request gitlab-org/gitlab!21572