Backport changes from introducing GithubService interation in EE

What

• Hides Triggers if integration only has one event
• Service integration displays validation errors on test fail
• Adds detailed_status to pipeline hook data
• Adds detailed_description option for Services
• Integration edit page renders 404 if a service is disabled

Why

Various changes were made in https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/4591 which CE can benefit from

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered
• End-to-end tests pass (package-qa manual pipeline job)

What are the relevant issue numbers?