Add branch existence check to the APIv4 branches via HEAD request

Closes #37159

See merge request !13979

Fix diff comment button not showing after deleting a comment

Closes #37142

See merge request !13997

Add my_reaction_emoji param to /issues and /merge_requests API

See merge request !14016

Extend API: Pipeline Schedule Variable

Closes #34518

See merge request !13653

Merge branch 'fix/sm/35650-remove-createtriggerrequestservice-and-forbid-to-persist-variables-on-ci-triggerrequest' into 'master'

Removes `CreateTriggerRequestService` and add a blocker to prevent saving variables on `Ci::TriggerRequest`

Closes #35650

See merge request !13792

Implement `failure_reason` on `ci_builds`

Closes #37239

See merge request !13937

Fix CI/CD `types` config entry removal due date

See merge request !13990

Added support for additional time series charts

Closes #33345

See merge request !13159

Make project selection dropdown for issue editing consistent

See merge request !13574

Make transfer project dropdown in project settings consistent

See merge request !13596

Make target branch dropdown on merge request edit page consistent

See merge request !13592

Make protected branches / tags permission dropdowns consistent

See merge request !13611

Make dropdowns on new issue page consistent

See merge request !13584

Make comment form dropdown style consistent

See merge request !13473

Avoid @extend for .text-danger in dropdowns

Closes #37396

See merge request !14030

Adds documentation to use Vuex

Closes #36070

See merge request !13931

Deprecate custom SSH client configuration for the git user

Closes #37204

See merge request !13930

Fix Import/Export spec failure

See merge request !14032

- Fix spec