Merge pull request #15434 from ktoso/port-persistenceId-ktoso

!per #15230 rename processorId => persistentId (for validation)
=per #15230 deprecate Channel and PersistentChannel

Conflicts:
	akka-persistence/src/main/scala/akka/persistence/Channel.scala
	akka-persistence/src/main/scala/akka/persistence/PersistentChannel.scala
	akka-persistence/src/test/scala/akka/persistence/serialization/SerializerSpec.scala