For each tracked entity, track the current revision ID of that entity.
Open question: what about invalidating constraint check results when a constraint statement is edited? Do we track the current revision ID of the property as well? Or can we do something more sophisticated? (With T182110: Only update constraints table when constraint statements were edited, we will in theory have the option to know which revisions actually changed the constraints and which didn’t, but we’d have to keep track of that somewhere.)