+per defer for PersistentActor

note: defer does not persist anything (does not even hit the journal). I think this is enough, as if someone wants to persist stuff (get replayable stuff), they can just use persist methods.

Refs #15299 
Depends on #15227

TODO: 
- [x] try to implement using same mechanisms as `persistAsync`, remove the 3rd state, make the Journal not persist `LoopStuff` wrapped messages.
- [x] update the persistence lambda docs
Hm yeah, that's a valid point.
In the previous impl we did not have to flush, and the `State` would take care of the stashig etc.

So I should unstash and try the "Resequencable but not for persisting" version you think? 
I have started on it previously.