Render calendar feed inline when accessed from GitLab

Closes #47672

See merge request gitlab-org/gitlab-ce!19698

Merge branch 'blackst0ne-rails5-expected-the-response-to-have-status-code-ok-but-it-was-404' into 'master'

Resolve "[Rails5] expected the response to have status code :ok but it was 404"

Closes #48008

See merge request gitlab-org/gitlab-ce!19937

Rails5 update Gemfile.rails5.lock

Closes #48009

See merge request gitlab-org/gitlab-ce!19921

Resolve "[Rails5] expected: "/search?search=seed_project" got: nil"

Closes #48013

See merge request gitlab-org/gitlab-ce!19936

[Rails5] Fix pipeline_schedules_controller_spec

Closes #48011

See merge request gitlab-org/gitlab-ce!19919

Expose a clean_backtrace method from Gitlab::Profiler

See merge request gitlab-org/gitlab-ce!19894

Rails5 fix update_attribute usage not causing a save

Closes #47960

See merge request gitlab-org/gitlab-ce!19881

[Rails5] Explicitly set request.format for blob_controller

Closes #47921

See merge request gitlab-org/gitlab-ce!19876

With text/calendar as Content-Type, the browser always downloads the
content as a file (even ignoring the Content-Disposition header). We
want to display the content inline when accessed from GitLab, similarly
to the RSS feed.

Resolve "Milestone not updating in MR sidebar after selection"

Closes #47933

See merge request gitlab-org/gitlab-ce!19870

Make Gitaly wiki RPC's mandatory

See merge request gitlab-org/gitlab-ce!19701

Fix queue_name in Rails 5

Closes #47372

See merge request gitlab-org/gitlab-ce!19874

Remove the ci_job_request_with_tags_matcher

See merge request gitlab-org/gitlab-ce!19947

Optimise paused runners

See merge request gitlab-org/gitlab-ce!19946

We have long polling mechanism which is not being used by paused runners.
This makes the paused runner to generate a request every 3s,
where it could be fired only every 1h.

Harmonize theme preferences previews

See merge request gitlab-org/gitlab-ce!19916

Since Rails 5 request.format gets set by extension if it's not explicitly
set.
That means artifacts_controller#file no longer works as expected.
This commit explicitly sets request.format for artifacts_controller#file.

Refactor sessions_controller_spec to work both in rails4 and rails5.
Remove the stubbed `request.referer` method, set real header instead.

In Rails 5.0 there's a bug [1] in controller tests that doesn't parse
nested parameters correctly.

This commit brings a workaround to make specs work again both in rails4
and rails5.

[1]: https://github.com/rails/rails/issues/23997

Resolve "BS4: Mini graph dropdown sometimes open on the top"

Closes #47610

See merge request gitlab-org/gitlab-ce!19912

Resolve "Pipeline dropdown shifts around at smaller screen sizes"

Closes #47068

See merge request gitlab-org/gitlab-ce!19910

Remove small container width

Closes #36439

See merge request gitlab-org/gitlab-ce!19893

Resolve "Wiki git clone holder and dropdown is broken"

Closes #47917

See merge request gitlab-org/gitlab-ce!19913

Enable no-multi-assignment in JS files

See merge request gitlab-org/gitlab-ce!19808

Resolve "Update link in GitLab cluster setup form to say "see pricing""

Closes #45557 and #47431

See merge request gitlab-org/gitlab-ce!19495

Resolve "Misalignment in rows on comparison page"

Closes #47879

See merge request gitlab-org/gitlab-ce!19909

Resolve "Stop horizontal scrolling when clicking on board issue"

Closes #46610

See merge request gitlab-org/gitlab-ce!19722

Merge branch '47975-project-select-dropdown-is-broken-for-group-issues-and-merge-requests' into 'master'

Resolve "Project select dropdown is broken for group issues and merge requests"

Closes #47975

See merge request gitlab-org/gitlab-ce!19906

Remove additional border from the create project page

Closes #47356

See merge request gitlab-org/gitlab-ce!19899

Partially addresses #47006.