[blob] Add support for removing holders by tags
Summary:
In D13646, a request format was extended to support removing holders by tags. Now server-side support is added.
Test Plan: Played with the DELETE /holders endpoint in Postman. Added some prefixed holders and verified that they were removed from DDB
Reviewers: kamil, varun, will
Reviewed By: kamil
Subscribers: ashoat, tomek
Differential Revision: https://phab.comm.dev/D13647