Add pause/resume button to project runners

What does this MR do?

Adds pause/resume buttons to a project's "Specific Runners" settings area for each runner as a shortcut/alternative to edit -> (un)check 'Active' -> save changes

Are there points in the code the reviewer needs to double check?

#resume and #pause already existed in Projects::RunnersController, but did not seem to be used for anything, so I commandeered them for this and changed their return path to send the user back to the project CI/CD settings.

(Tests already exist for those endpoints as well, which is why I'm not adding any tests in this MR)

Why was this MR needed?

See #20035 (closed) It's just a convenience

Screenshots (if relevant)

Pause: Resume:

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

What are the relevant issue numbers?

Closes #20035 (closed)