Revert "Merge branch 'revert-2c879643' into 'master'"

See merge request !12870

This reverts merge request !12633

Update the mysql2 gem to v0.4.5

See merge request !12859

Instrument Ability

See merge request !12865

Gitlab::Git shuffling and Gitaly annotations

See merge request !12849

Extract partials from the protected_branches & protected_tags views

See merge request !12864

Move find file URL out of global variable

See merge request !12846

Fixes needed when GitLab sign-in is not enabled

See merge request !12491

Fix spacing in sidebar

Closes #35035

See merge request !12844

So they are reusable for EE later

Fixed typo

See merge request !12862

Handle case when BroadcastMessage.current is nil

Closes #35094

See merge request !12860

Somehow Rails.cache.fetch occasionally returns `nil` values, which causes
this endpoint to crash.

Closes #35094

Make sure MergeRequest commit methods work when either compare_commits or merge_request_diff is set

Closes #35077

See merge request !12856

Increase width of dropdown menus

Closes #34989

See merge request !12809

Supplement Portuguese Brazil translation of Project Page & Repository Page

Closes #33672

See merge request !12156

Reload page after changing navigation preference

Closes #34968

See merge request !12833

Add more notes about developer seeds

See merge request !12836

Backport MR create service changes from EE

See merge request !12808

Part of #34903

When sign-in is disabled:
 - skip password expiration checks
 - prevent password reset requests
 - don’t show Password tab in User Settings
 - don’t allow login with username/password for Git over HTTP requests
 - render 404 on requests to Profiles::PasswordsController

Prevent GitLab issue tracker spec from failing later specs

Closes #35042

See merge request !12835

Enable all feature flags by default in specs

See merge request !12832

Otherwise some features would go untested in non-specific contexts

I did need to disable the
`gitlab_git_diff_size_limit_increase`-feature in some specs since we
depend on diffs being expandable while the file we are testing on is
smaller than the increased limit.

Fix links to documentation describing the Prometheus service and its specifics.

Closes #34598

See merge request !12714

Truncate job on environment view

Closes #34835

See merge request !12818