Pick security fixes from 8.16.1 et al into master

Closes #26813, #26249, #26259, #26243, #26242

See merge request !8724

Rename endboss -> maintainer, miniboss -> reviewer

See merge request !8719

Handle unsubscribe notification via email

Closes #22619

See merge request !6597

Allow creating protected branches when user can merge to such branch

Closes #22638

See merge request !8458

Remove rogue scrollbars from some issue comments

Closes #25989

See merge request !8652

Allow issue filter submission using mouse only

See merge request !8681

Upgrade OmniAuth Ruby gem to 1.3.2

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/26813

See merge request !2056

Prevent users from creating notes on resources they can't access

See https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/2054

Ensure that only privileged users can access merge requests in the API

See merge request !2053

Fix export files not removed when a user takes over a namespace

See merge request !2051

Fix users being able to delete instance public deployment keys

See merge request !2049

adds events to services api deserialization

Closes #22974

See merge request !8324

Add hover style for copy icon in commit page header

Closes #26787

See merge request !8619

Use a warning icon for a stage with allowed to fail builds

Closes #21948

See merge request !8503

Change twitter likes URL in README

See merge request !8702

Use archived trait for project in specs instead model column

See merge request !8635

Mattermost fixes

See merge request !8654

correct the prometheus feature configuration according to https://gitlab.com/git…

See merge request !8703

Change hover style definition from explicit rgba value to variable

Removed style from page-header.scss that was overriding .btn styles

Add hover style for copy icon in commit page header

Change hover style definition from explicit rgba value to variable

Removed unnecessary styles on commits.scss

correct the prometheus feature configuration according to https://gitlab.com/gitlab-org/omnibus-gitlab/blob/master/files/gitlab-config-template/gitlab.rb.template#L1147

Make cycle_analytics_events_spec.rb side-effect free

Closes #26622

See merge request !8594

Change the twitter `/favorites` to `/likes`

Merge request widget class names update

See merge request !8700

[ci skip]

Replace merge request widget body

See merge request !8697

Add Prometheus docs

See merge request !8699

[ci skip]

Fixed bug with merge immediately button not working

See merge request !8696

[ci skip]

Replaces https://gitlab.com/gitlab-org/omnibus-gitlab/merge_requests/1237
Omnibus MR: https://gitlab.com/gitlab-org/omnibus-gitlab/merge_requests/1227
Omnibus issue: https://gitlab.com/gitlab-org/omnibus-gitlab/issues/1481

This was caused by using 'this' in a fat arrow function, so 'this' would not equal the jQuery element

Update autodeploy templates [ci skip]

See merge request !8695