+per #15424 Added PersistentView, deprecated View

A PersistentView works the same way as View did previously, except:

* it requires an `peristenceId` (no default is provided)
* messages given to `receive` are NOT wrapped in Persistent()

akka-streams not modified (PersistentPublisher).

Also solves #15436 by making persistentId in PersistentView abstract.