Review handling of deleted monograph parts in open-ils.circ.holds.retrieve_all_from_title

[Galen Charlton]

Currently, open-ils.circ.holds.retrieve_all_from_title will retrieve all active part holds on a title, even if the part has been deleted.

While ideally such holds should not exist, at present there's nothing in Evergreen to stop deleting a part that has holds that target it.

It looks like that open-ils.circ.holds.retrieve_all_from_title will _not_ return holds that are targeting deleted items or call numbers, so there is an inconsistency here. Also, the routine will return partial results if it happens to encounter a situation where the title has no active call numbers or items.

At the moment, the only active internal consumer of this method is the routine that handles retargeting holds during checkin.

I'm filing this bug as a signal that I'm getting some questionable code smells from this routine, but not that I've (yet) found a specific user-visible problem.