[ci] Doxygen warnings
- Fixes "Job's log exceeded limit of 4194304 bytes." by reducing Doxygen output
- Shows warnings on the job log
- Introduces number of Doxygen warnings as a CI metric
@endJunction Not related to this MR but you now can see code coverage percentage in the merge / pipeline widget.
- Feature description was added to the changelog
- Tests covering your feature were added?