Add /-/readiness /-/liveness and /-/health_metrics endpoints to track application readiness

Closes #24240

See merge request !10416

Add auto-cancel for pending pipelines on branch, if they are not HEAD

See merge request !9362

Fix markdown table in API Issues docs

See merge request !10500

Adds polling function to pipelines table

Closes #5983

See merge request !10210

Update Prometheus documentation for 9.1

See merge request !10516

* upstream/master: (58 commits)
  Fix icon name error
  Rewrite system note helper
  Change edit icon
  Leave icon area blank if legacy note; remove diamond icon
  Fix positioning of note icons
  Fix newline errors
  Add remaining system note icons
  Add system notes icon helper; add icons
  Fixed specs Updated JS that was causing the hints to appear & then disappear
  Update tests
  Fix broken spinach test
  Reuse code
  Improve shortcuts code
  Adds ShortcutsDashboardNavigation to globals comment since its a global variable
  Fix shortcut specs
  Reorganize shortcut help menu
  Change todos shortcut to shift
  Change shortcuts
  Switch global shortcuts to shift; reuse key styles from help menu
  Map bindings to lowercase letters; only show key bindings when using keyboard shortcut
  ...

Stop new merge request page tabs updating the URL

Closes #30419

See merge request !10471

Removes unused code

See merge request !10456

View helpful system note in comment threads

Closes #24784

See merge request !10503

Add keyboard shortcuts to main menu.

Closes #30036

See merge request !10243

Button capitalisation

Closes #18931

See merge request !10418

Fix container going full-width when switching from "Side-by-side" "Changes" MR tab before done loading

Closes #29193

See merge request !10172

Updated JS that was causing the hints to appear & then disappear

1. Show shortcuts for easy navigation.