Reduce cardinality of some of GitLab's Prometheus metrics and fix observed duration reporting.

Closes #41045

See merge request gitlab-org/gitlab-ce!15881

Fall back to the `MergeRequestWidgetEntity`

Closes #41296

See merge request gitlab-org/gitlab-ce!16074

Resolve "Decouple multi-file editor from file list"

Closes #40040 and #40032

See merge request gitlab-org/gitlab-ce!15430

organise content by subject

See merge request gitlab-org/gitlab-ce!16080

When no serializer was passed.

LDAP extern_uids are not normalized when updated via API

Closes #40279

See merge request gitlab-org/gitlab-ce!16004

Add CI YML example for Browser Performance Testing in CE

See merge request gitlab-org/gitlab-ce!16058

Resolve "Docker volumes not mounted when using docker:dind"

See merge request gitlab-org/gitlab-ce!16070

Restore missing language code in datetime_utility.js

Closes #41248

See merge request gitlab-org/gitlab-ce!16009

Remove two unused step definitions from spinach

See merge request gitlab-org/gitlab-ce!16047

Hide toolbar in markdown preview mode

Closes #40063

See merge request gitlab-org/gitlab-ce!15994

Add support for defining explicit dependencies to QA factories

Closes gitlab-qa#122

See merge request gitlab-org/gitlab-ce!15979

Remove a redundant `InvalidPathError` definition

See merge request gitlab-org/gitlab-ce!16064

Add new last_commit_id param for create commit endpoint

Closes #38356

See merge request gitlab-org/gitlab-ce!15922

Enables ordering groups and their children by name in the web interface

Closes #24962 et #36958

See merge request gitlab-org/gitlab-ce!16045

Fix racing condition in Ajax call of merge_request_tabs_spec.js

Closes #35294

See merge request gitlab-org/gitlab-ce!16012

Merge branch '41291-spec-failure-on-spec-features-merge_requests-image_diff_notes_spec-rb' into 'master'

Fix a failure because we stub DiffHelper#diff_file_blob_raw_path instead of #diff_file_blob_raw_url

Closes #41291

See merge request gitlab-org/gitlab-ce!16052

This is already defined in `ExtractsPath`, which this controller
includes.

Update d3 to v4 to enable tree shaking (and reduce the size of our webpack bundles)

Closes #37013

See merge request gitlab-org/gitlab-ce!15585

Revert "Move Repository#write_ref to Git::Repository#write_ref"

Closes #41143

[ci skip]

See merge request gitlab-org/gitlab-ce!16055

Migrate to Project#empty_repo?

Closes #41326

See merge request gitlab-org/gitlab-ce!16054

This reverts merge request !15712

Signed-off-by: Rémy Coutable <remy@rymai.me>

- Apply some refactoring for code reuse
- Add file status validation for Files::DeleteService
- Write additional specs