As I hub administrator, I need to be able to permanently delete collection that aren't used by any other collections in the system along with and all of its versions.

This endpoint must:

• Verify that the collection isn't depended on by other collections
• Remove the collection version from all repos it's in
• Delete repo version history for all repos the collection version was ever in
• Perform orphan cleanup.

See https://docs.google.com/document/d/1w-bP7U2aJ6m1Qa__8vCrlY8tJcNlNiK03ad51Pp0-FQ/edit#heading=h.115vdb79z615 for implementation details.