Add applications section to GKE clusters page

See merge request gitlab-org/gitlab-ce!15064

CE repository mirroring changes backport

See merge request gitlab-org/gitlab-ce!15184

Added discussion_line_code value to note response and use it to query the right…

Closes #38677

See merge request gitlab-org/gitlab-ce!14981

Merge remote-tracking branch 'origin/refactor-clusters' into 36629-35958-add-cluster-application-section

Merge remote-tracking branch 'origin/38464-k8s-apps' into 36629-35958-add-cluster-application-section

Merge branch 'fix/sm/37299-environments-validate-uniqueness-on-url-and-can-cause-silent-deployment-failures' into 'master'

Remove unique validation from external_url in Environment

Closes #37299

See merge request gitlab-org/gitlab-ce!15202

Fix cron_parser_spec.rb (`master` branch failure on Nov 5th)

Closes #39817

See merge request gitlab-org/gitlab-ce!15196

Resolve "Expose project visibility as CI variable"

Closes #37473

See merge request gitlab-org/gitlab-ce!15193

Fix a migration that adds merge_requests_ff_only_enabled column to MR table

Closes #39382 and #39357

See merge request gitlab-org/gitlab-ce!15195

Replace PhantomJS with Headless Chrome for GitLab Integration Tests

Closes #30876

See merge request gitlab-org/gitlab-ce!12244

Fix clusters description text collapsing away on page-load

Closes #39771

See merge request gitlab-org/gitlab-ce!15177

* master: (33 commits)
  Ignore SQL CACHE hits in Sherlock
  Fix SQL timings for the performance bar
  Find the LFS-objects for a fork within a the fork network
  Remove bottom-border from last responsive table row
  Add system hooks user_rename and group_rename
  Unlink a project from a fork network when it's source was deleted.
  Make sure the settings page renders when root of a fork is deleted
  Remove Peek's original keyboard shortcut (numpad 0, keycode 96)
  Add application setting to Auto DevOps docs
  Enable MergeableSelector in scss-lint (for !14567)
  Enable MergeableSelector in scss-lint (for !14055)
  Enable MergeableSelector in scss-lint (for !14062)
  Enable MergeableSelector in scss-lint (for !14398)
  Enable MergeableSelector in scss-lint (for !13480)
  Enable MergeableSelector in scss-lint (for !13473)
  Enable MergeableSelector in scss-lint (for !13600)
  Enable MergeableSelector in scss-lint
  Resolve ""To do" should be "Todos" on Todos list page"
  Avoid regenerating the ref path for the environment
  Remove white space at bottom of issue boards
  ...

Fix Gitlab::Metrics::System#real_time and #monotonic_time doc

See merge request gitlab-org/gitlab-ce!15187