[Backport] EE's Burndown chart for group milestone common code

See merge request gitlab-org/gitlab-ce!18511

Expose Deploy Token info as environment variables to CI/CD jobs

Closes #44447

See merge request gitlab-org/gitlab-ce!18414

Fix users not seeing labels from private groups when being a member of a child project

Closes #45463

See merge request gitlab-org/gitlab-ce!18544

Fix docs typo in Validate the .gitlab-ci.yml

Closes #45688

See merge request gitlab-org/gitlab-ce!18552

Add Capybara debugging methods to docs

See merge request gitlab-org/gitlab-ce!18549

[ci skip]

Add changelog entry for updating doorkeeper

See merge request gitlab-org/gitlab-ce!18550

Update links to /ci/lint with a new project's ci/lint

Closes #45666

See merge request gitlab-org/gitlab-ce!18539

Resolve "Avatar URLs are wrong when using a CDN path and Object Storage"

Closes #44775

See merge request gitlab-org/gitlab-ce!18092

Update doorkeeper

Closes #45433 and #45647

See merge request gitlab-org/gitlab-ce!18543

https://gitlab.com/gitlab-org/gitlab-ce/issues/45433
and
https://github.com/doorkeeper-gem/doorkeeper/issues/1065

Resolve "Namespace factory is problematic"

Closes #42936

See merge request gitlab-org/gitlab-ce!18464

Resolve "Repository storages documentation URL moved"

Closes #45635

See merge request gitlab-org/gitlab-ce!18529

Resolve "Skip setup of gitlab-shell, gitaly, ... for specs that don't need it."

Closes #44713

See merge request gitlab-org/gitlab-ce!18074

Added missing note for P1 priority and updated links

See merge request gitlab-org/gitlab-ce!18491