+per #13944 Send RecoveryComplete message at end of recovery

Fixes #13944

Conflicts:
	akka-docs/rst/scala/code/docs/persistence/PersistenceDocSpec.scala
	akka-persistence/src/main/scala/akka/persistence/Processor.scala
	project/AkkaBuild.scala
Merge pull request #15385 from akka/wip-13944-send-marker-message-after-recovery-finished-master-ban

+per #13944 Send RecoveryComplete message at end of recovery (Validation)