=act #13966 Change wrong default discardOld in UntypedActor become
Merge pull request #15068 from akka/wip-13966-become-discardOld-patriknw

=act #13966 Change wrong default discardOld in UntypedActor become
!str #15063 Add Flow.Transformer interface

* Skip wrapping RecoveryTransformer elements in Try
* this will make it possible to use the same RecoveryTransformer interface
  for javadsl and scaladsl, which is important if we package building
  blocks in Transformer classes
* also avoids wrapper allocation