Add new API endpoint - list jobs of a specified runner
What does this MR do?
Adds new API endpoint that allows to list all running jobs assigned to a specified Runner.
Are there points in the code the reviewer needs to double check?
Why was this MR needed?
Please read #39699 for a reference.
Screenshots (if relevant)
Does this MR meet the acceptance criteria?
- Changelog entry added, if necessary
- Documentation created/updated
- API support added
- Tests added for this feature/bug
- 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?