Add rake task to delete orphan artifact objects

What does this MR do and why?

This adds the 2nd rake task gitlab:cleanup:delete_orphan_job_artifact_final_objects that will process the generated list of orphan objects from gitlab:cleanup:list_orphan_job_artifact_final_objects and deletes each of then from storage.

This rake task will process the orphans list file and will delete each object from storage. All deleted objects are then logged into a separate file with the filename format of deleted_from--<orphans_list_filename>.