=per #15520 make Persist1CommandProcessor in benchmark  extends Persiste...

sorry for my previous PR https://github.com/akka/akka/pull/15517 not that right,I corrected this via this one.
now the Persist1CommandProcessor extends the PersistentActor and not ```persist```message.
This has different semantics.

`Persist1Command` is meant to use the `Processor` because we wanted to benchmark the `PersistentActor` vs. the `Processor` so that we know the performance is roughly the same.

No need for this change at this point, but thanks for looking into it! // We will remove Processor once we start deleting the deprecated classes.