Introduce the following variables

- CI_MERGE_REQUEST_ID
- CI_MERGE_REQUEST_IID
- CI_MERGE_REQUEST_REF_PATH
- CI_MERGE_REQUEST_PROJECT_ID
- CI_MERGE_REQUEST_PROJECT_PATH
- CI_MERGE_REQUEST_PROJECT_URL
- CI_MERGE_REQUEST_TARGET_BRANCH_NAME
- CI_MERGE_REQUEST_SOURCE_PROJECT_ID
- CI_MERGE_REQUEST_SOURCE_PROJECT_PATH
- CI_MERGE_REQUEST_SOURCE_PROJECT_URL
- CI_MERGE_REQUEST_SOURCE_BRANCH_NAME

Resolve "Include tags into pipeline detail view"

Closes #54336

See merge request gitlab-org/gitlab-ce!23364

Fixed expanding diff commit files

Closes #50662

See merge request gitlab-org/gitlab-ce!23591

Add new Korean and Polish proofreaders

See merge request gitlab-org/gitlab-ce!23594

Change container width for project import

See merge request gitlab-org/gitlab-ce!23318

Replace admin sidebar feature spec with view spec

See merge request gitlab-org/gitlab-ce!23551

Add UsageData for group/project clusters

Closes #54886

See merge request gitlab-org/gitlab-ce!23590

Use group clusters when deploying (DeploymentPlatform)

See merge request gitlab-org/gitlab-ce!22308

Resolve "Searching users by the admin panel wipes query when using sort"

Closes #50626

See merge request gitlab-org/gitlab-ce!23439

Removed the merge-train script

See merge request gitlab-org/gitlab-ce!23587

Rename project's pipelines relation

See merge request gitlab-org/gitlab-ce!23353

Fixed multiple discussions getting added to diff lines

Closes gitlab-ee#8195

See merge request gitlab-org/gitlab-ce!23541

Improve help and validation sections of maximum build timeout inputs

Closes #49434

See merge request gitlab-org/gitlab-ce!23586

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/50662

Avoid 500's when serializing legacy diff notes

Closes #54793

See merge request gitlab-org/gitlab-ce!23544

We're moving the automatic merging logic to a separate repository, so
there's no need in keeping this file around.

[ci skip]

[Backport] Extract system check rake task logic

See merge request gitlab-org/gitlab-ce!23395

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/8195

Resolve "Use read_repository scope on read-only files endpoints"

Closes #54826

See merge request gitlab-org/gitlab-ce!23534

Remove merge:master job entirely

See merge request gitlab-org/gitlab-ce!23585

Apparently disabling it by checking for a variable doesn't actually
disable it.

[ci skip]

Fix list that doesn't render properly

See merge request gitlab-org/gitlab-ce!23574

Setup Jest test environment

See merge request gitlab-org/gitlab-ce!23406

fix: update the link to the new address.

See merge request gitlab-org/gitlab-ce!23524

Merge request pipelines

See merge request gitlab-org/gitlab-ce!23217

Don't request changelog for MR with 'meta' label

See merge request gitlab-org/gitlab-ce!23556

Extract code into IssueBoardEntity / serializer (follow up)

See merge request gitlab-org/gitlab-ce!23511

Add example email on push notification to docs

See merge request gitlab-org/gitlab-ce!23566

Namely the `ci-build` and `meta` labels.
Signed-off-by: Rémy Coutable <remy@rymai.me>