R1:18da346972b6

Add additional flags to "bin/repository rebuild-identities" to improve flexibility

Summary:
Ref T13444. Repository identities have, at a minimum, some bugs where they do not update relationships properly after many types of email address changes.

It is currently very difficult to fix this once the damage is done since there's no good way to inspect or rebuild them.

Take some steps toward improving observability and providing repair tools: allow `bin/repository rebuild-identities` to effect more repairs…