PlantUML support for Markdown

Closes #4048

See merge request !8588

Backport changes from EE squash

See merge request !8912

replace `find_with_namespace` with `find_by_full_path`

See merge request !8949

Force new password after password reset via API

Closes #24606

See merge request !8933

Backport changes from the EE-only squash implementation, which would
otherwise conflict when merge CE into EE.

<https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1024>

Update installation docs to include Docker, others

See merge request !8943

add complete changelog for !8949

Allow rendering of PlantUML diagrams in Markdown documents using fenced blocks:

    ```plantuml
    Bob -> Sara : Hello
    Sara -> Bob : Go away
    ```

Closes: #4048

Don't execute git hooks if you create branch as part of other change

Closes #23439

See merge request !7237

Backport frontend test fixes from webpack branch

See merge request !8945

Ignore node_modules in rubocop

See merge request !8942

Don't require lib/gitlab/request_profiler/middleware.rb in config/initializers/request_profiler.rb

Closes #20452

See merge request !8927

Resolve "Comment button doesn't align vertically with line number"

Closes #26859

See merge request !8918

Resolve "Comment button doesn't align vertically with line number"

Closes #26859

See merge request !8918

Fix Ruby verification command

See merge request !8938

Resolve "Double separator line in Edit projects settings"

Closes #27321

See merge request !8917

Simplify the SSH protocol introduction and link to a DO tutorial

See merge request !8901

As per this comment
https://gitlab.com/gitlab-com/support/issues/374#note_22056587 we're
moving documentation around from the support workflows.

Fix wrong call to ProjectCacheWorker.perform, and call ProjectCacheWorker.perform_async instead

Closes #27516

See merge request !8910

Fixed group label in issuable sidebar

Closes #27253

See merge request !8924