[master] Prevent project creation (blank, import or fork) when repository already exists on disk

See merge request gitlab/gitlabhq!2169

We need to cleanup after each execution so we can still re-use the same
paths and prevent collision with the on disk validation

Replace 'project/user_lookup.feature' spinach test with an rspec analog

See merge request !13863

Resolve "Mysql2::Error: Unknown column 'award_emoji.count' on master"

Closes #37231

See merge request !13926

Resolve "README.md: Header image scale not limited"

Closes #37058, #37024, and #37230

See merge request !13869

As we only override in two places, we could just ask for the value rather than
the method name.

Move GPG signed commits docs to new location

Closes #36804

See merge request !13872

Update backup_restore.md documentation regarding S3 and IAM profiles.

See merge request !13871

Perf.slow issuable

Closes #32844

See merge request !13685

Improve AutocompleteController#users.json performance

Closes #36879

See merge request !13754

Postgres lets you treat `count` as another alias for `COUNT(*)` apparently, even
if that's not the actual alias used.

Fixes the margin of the top buttons of the pipeline page

Closes #34990

See merge request !13908

Respect the default visibility level when creating a group via the API

Closes #37198

See merge request !13903

API: Respect the 'If-Unmodified-Since' for delete endpoints

See merge request !9621

Make file template dropdowns consistent

See merge request !13577

Make profile settings dropdown consistent

See merge request !13623

Backports EE 2756 logic to CE.

See merge request !13892

Make notification dropdowns consistent

See merge request !13624

max-width for lazy-loaded images (this was removed in the original MR through merge resolution most probably)

Better align fallback image emojis

Closes #37147

See merge request !13881

Make Identicon for avatars a shared component

Closes #35010

See merge request !13919

Make issuable dashboard dropdowns consistent

See merge request !13594

Port translations from EE to CE

See merge request !13918

Add filter by my reaction

Closes #35618

See merge request !12962

Merge branch 'pawel/bump_prometheus_client_mmap_version_to_fix_performance_degradation' into 'master'

Update Prometheus Client MMAP gem to version that fixes performance degradation

See merge request !13898

Add Geo to the list of team labels

See merge request !13896

Eager load head pipeline projects for MRs index

See merge request !13877

New Crowdin translations

See merge request !2743

Replace 'project/star.feature' spinach test with an rspec analog

See merge request !13855

Fix broken Frontend JS guide

See merge request !13912