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 and operate on identities more surgically.

Test Plan: Ran bin/repository rebuild-identities with all new flags, saw what looked like reasonable rebuilds occur.

Maniphest Tasks: T13444

Differential Revision: https://secure.phabricator.com/D20911