Clean up dependency proxy blobs from deleted groups
The following discussion from !27843 (closed) should be addressed:
This is not in scope for the MR but curious: are we handling cleanup for previously deleted groups?
If a group with a dependency proxy enabled has been deleted, until !27843 (closed) the underlying cached blobs for the group were not getting removed.
This issue is a follow up to create a cleanup migration to remove orphaned blobs.