SubscriberHistory does not declare uuid entity key

I updated the title as it's different from #3266989 - the SubscriberHistory entity currently doesn't even have a uuid field.

I didn't put a UUID for the reason that the entity doesn't seem to identify anything concrete. Equally a revision doesn't have a UUID. I am open to changing it, but we need to make sure it doesn't have a cost for the majority of sites that don't need it.

We import users, webform submissions and newsletter subscriptions from different sites into one backend using default_content_deploy. So we need a UUID field to avoid id collisions.

This works well for everything except the SubscriberHistory. With that patch applied, SubscriberHistory works as well.

But I agree that the update hook requires a batch.