Add Troubleshooting section for Merge Train documentation

Closes #64948

See merge request gitlab-org/gitlab-ce!31033

Add trouble shooting sections

Update links to relative

Closes #61945

See merge request gitlab-org/gitlab-ce!31084

Following the single docs codebase change, all internal links
should be relative. Also cleans up one table

Resolve "Incorrect message interpolation on project listing"

Closes #65088

See merge request gitlab-org/gitlab-ce!31121

Logging sidekiq worker class name in SidekiqMemoryKiller

See merge request gitlab-org/gitlab-ce!30996

Fix outbound_local_requests_whitelist nil for existing ApplicationSetting records

Closes #65096

See merge request gitlab-org/gitlab-ce!31123

It needs to default to an empty array logically.

Add doc about incident issue labels

See merge request gitlab-org/gitlab-ce!31107

Add `Incident` label to issues created by the Alert Bot

See merge request gitlab-org/gitlab-ee!14705

Create a label named `incident` if missing.

Add namespace label toggle

See merge request gitlab-org/gitlab-ce!30935

Added the ability to update the namespace label text for gitlab-managed

Add frozen_string_literal to spec/support

See merge request gitlab-org/gitlab-ce!31132

Remove \ from unicorn\_stderr.log

See merge request gitlab-org/gitlab-ce!31159

Merge branch '13038-geo-gitlab-geo-databasetasks-pending_migrations-returns-migrations-already-applied' into 'master'

Resolve "Geo - Gitlab::Geo::DatabaseTasks.pending_migrations returns migrations already applied"

Closes #13038

See merge request gitlab-org/gitlab-ee!14831

Support title and desc on merge w/ push option

See merge request gitlab-org/gitlab-ce!31068

Resolve "table_exists? not compatible with Rails 5.1"

Closes #54478

See merge request gitlab-org/gitlab-ce!30832

[EE] Resolve "table_exists? not compatible with Rails 5.1"

See merge request gitlab-org/gitlab-ee!14717

Remove duplicate content about auto-devops customization

See merge request gitlab-org/gitlab-ce!30929

Update guidance for EE doc submissions

See merge request gitlab-org/gitlab-ce!31042

Note GitLab University may be out of date in parts

See merge request gitlab-org/gitlab-ce!31034

Update documentation for current state

Closes #64710

See merge request gitlab-org/gitlab-ce!30873

Stop printing dots while retrieving pod in review-apps.sh

See merge request gitlab-org/gitlab-ce!31062

Improve steps for setting commit email

Closes #54881

See merge request gitlab-org/gitlab-ce!30833