Merge branch '439042-refactor-scheduling-worker-into-a-service' into 'master'

Refactor Zoekt::SchedulingWorker into a service

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/142909



Merged-by: Madelein van Niekerk <mvanniekerk@gitlab.com>
Approved-by: Greg Alfaro <galfaro@gitlab.com>
Approved-by: Ravi Kumar <rkumar@gitlab.com>
Approved-by: Madelein van Niekerk <mvanniekerk@gitlab.com>
Reviewed-by: Dmitry Gruzd <dgruzd@gitlab.com>
Co-authored-by: Dmitry Gruzd <dgruzd@gitlab.com>