* re-implement javadsl testkit
* fix mima problem
* rebase master
* move ImplicitSender/DefaultTimeout to scaladsl
* undo the change of moving scala api
* fix return type and add doc
* resolve conflicts and add more comments
* Verify that it actually fails with classic remoting
if vector clocks are not pruned
* Make it pass with Artery, but it is not verifying
the message sizes yet. We should implement that
with a custom RemoteInstrument, but that can be done
in separate PR.
* Still pending with Artery because it still fails on jenkins
* barrier after sys shutdown
(cherry picked from commit d5edcbea35ca5b43ca4cfb3018602dd555402f42)
