Implement UX designs for rate-limited webhooks

This relates to work in &6004 to improve the reliability of webhooks.

To do so, we need to inform users when their webhooks have been rate limited.

Designs

See: #331407[Scenario_3.png]

To Do

• Add danger alert (dismissible) to project/group/admin webook edit pages
  • app/views/projects/hooks/edit.html.haml
  • ee/app/views/groups/hooks/edit.html.haml
  • app/views/admin/hooks/edit.html.haml

  Webhook was automatically disabled
  
  The webhook was triggered more than %{x} times per minute and is now disabled. To re-enable this webhook, fix the problems shown in **Recent events**, then re-test your settings. [Contact Support](https://support.gitlab.com/hc/en-us/requests/new) if you need help re-enabling your webhook.

• Add danger badge to app/views/shared/web_hooks/_hook.html.haml

  Disabled