Add systemd service for scm delayed job queue

The `ReportToScmJob` (responsible for reporting back the resulting
build states of a Workflow to GitHub/GitLab) queues the jobs
in a dedicated delayedjob queue.

Co-authored-by: Dany Marcoux <dmarcoux@suse.com>
Co-authored-by: Victor Pereira <vpereira@suse.com>