R1:f8d6b6181eb4

Use PhabricatorCachedClassMapQuery when querying object PHID types

Summary:
Ref T11954. When we query for Conduit tokens, we load the associated objects (users) by PHID.

Currently, querying objects by PHID requires us to load every PHIDType class, when we can know which specific classes we actually need (e.g., just `UserPHIDType`, if only user PHIDs are present in the query).

Use PhabricatorCachedClassMapQuery to reduce the number of classes we load on this pathway.

Test Plan:
- Used `ab -n100` to…