Refactor discussions/notes code

Closes #42148

See merge request gitlab-org/gitlab-ce!17926

Resolve "Disabling two factor authentication via gitlab-rake fails"

Closes #44425

See merge request gitlab-org/gitlab-ce!18154

[Rails5] Allow using `RAILS5` env with rspec

See merge request gitlab-org/gitlab-ce!18140

Re-enable allowing n+1 Gitaly for branches index

Closes #44861

See merge request gitlab-org/gitlab-ce!18131

* ask_to_continue
* Gitlab::TaskAbortedByUserError

Use project path in package-and-qa to fetch script

See merge request gitlab-org/gitlab-ce!18145

Fix wrong error handling in update page service

Closes #44817

See merge request gitlab-org/gitlab-ce!18098

Add documentation about backporting changes from EE to CE

See merge request gitlab-org/gitlab-ce!18003

Always allow the performance bar to be enabled for admins

See merge request gitlab-org/gitlab-ce!18137

Replace the `project/issues/labels.feature` spinach test with an rspec analog

See merge request gitlab-org/gitlab-ce!18126

Resolve "Wrong user in push notification email"

Closes #44921

See merge request gitlab-org/gitlab-ce!18148

This was sending the current user, which is the recipient! It should be the user
who pushed the commits.

Do not retry package-and-qa manual action on failure

Closes #44882

See merge request gitlab-org/gitlab-ce!18130

Replace the `project/issues/issues.feature` spinach test with an rspec analog

See merge request gitlab-org/gitlab-ce!17950

Move Sidekiq exporter logs to log/sidekiq_exporter.log

See merge request gitlab-org/gitlab-ce!18127

[Rails5] Isolate `test_after_commit` gem

See merge request gitlab-org/gitlab-ce!18129

Whenever cache is enabled and cold, branches index still makes
n+1 calls. Make sure we catch this.

Backport missing object storage worker specs

See merge request gitlab-org/gitlab-ce!18138

Refactor the browser performance testing docs

See merge request gitlab-org/gitlab-ce!18097

Raise more descriptive errors when URLs are blocked

See merge request gitlab-org/gitlab-ce!18058

Resolve "Clicking confidential and lock icons on sidebar should also activate dropdown"

Closes #40907

See merge request gitlab-org/gitlab-ce!17869

Add button type to settings toggle

Closes #44737

See merge request gitlab-org/gitlab-ce!18134

Update brakeman to 4.2.1

Closes #44878

See merge request gitlab-org/gitlab-ce!18122

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

The Sidekiq exporter logs were mixing with the normal Sidekiq logs. In order
to support structured logging in Sidekiq, we either need to split this data
out or convert the exporter to produce structured logs. Since Sidekiq job
processing is fundamentally different information from Web server traffic,
it seems cleaner to move the metrics traffic into a separate file, where they
can be parsed by a different filter if needed.

Relates to #20060

Provide clarification on mirrored repositories for pipelines

See merge request gitlab-org/gitlab-ce!18105

Refactor the LFS S3 docs

See merge request gitlab-org/gitlab-ce!18029