!str #15964 Remove dependency to persistence

* It will show up again in the right place, in enhanced form, by #16541
Merge pull request #16544 from akka/wip-15964-remove-persistence-dependency-patriknw

!str #15964 Remove dependency to persistence
!str #16400 Add Java API for StreamTcp

* move io.StreamTcp to scaladsl.StreamTcp
* add javadsl.StreamTcp that delegates to scaladsl implementation
* move impl
* add java test