+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
I think that `WriteMessages` should take a `Seq[InSequence]` (or whatever the marker trait should be called) that is either a `Write(persistentRepr)` or a `Loop(message)` and then they are treated correctly in the journal as either a write or a loop.