R1:41f143f7feeb

Respect repository identities when figuring out authors/committers in Herald pre-commit hook rules

Summary:
Ref T13480. Currently, Herald commit hook rules use a raw address resolution query to identify the author and committer for a commit. This will get the wrong answer when the raw identity string has been explicitly bound to some non-default user (most often, it will fail to identify an author when one exists).

Instead, use the "IdentityEngine" to properly resolve identities.

Test Plan: Authored a…