R1:1667acfa5d71

Implement "PolicyInterface" on "UserEmail" so "EmailQuery" can load them properly

Summary:
See PHI1558. Ref T11860. Ref T13444. I partly implemented PHIDs for "UserEmail" objects, but they can't load on their own so you can't directly `bin/remove destroy` them yet.

Allow them to actually load by implementing "PolicyInterface".

Addresses are viewable and editable by the associated user, unless they are a bot/list address, in which case they are viewable and editable by administrators (in preparation for…