The ActorNormalization factory methods create
UserIdentityValue from the database rows, either via
fields of a joined table, or via a row from actor table.
They assume that the actor_id exist and throw othervise.
ActorNormalization is a storage-layer service providing
access to finding and acquiring actor_id.
The UserIdentityLookup methods do not instantiate new actor
on demand, they just find an appropriate row in the actor
table and return the result.
Bug: T272689
Depends-On: I74d81f3f0233efb17fc8df5178e4c477cc669c6f
Change-Id: Icfa1daca960c696a8cef8adab5eab53985802858
8d2c674ab0