Share same instance of deadLetters between LARP and RARP, see #2983
Generate ChildTerminated from all Terminated in RemoteDeploymentWatcher, see #2983

* The problem is that we do remote deployment to a node that isn't alive and with ordinary
  remoting that is not detected at all, as we know. With cluster this was taken care of by
  a later AddressTerminated and ChildTerminated generated by RemoteDeploymentWatcher. With
  the new RemoteDeadLetters the additional watch triggers an immediate Terminate which is
  captured by RemoteDeploymentWatcher but not acted upon since it's not an addressTerminated.
  RemoteDeploymentWatcher unwatch and will therefor not act on later AddressTerminated.
* The long term solution is to have reliable system messages and remote supervision without
  explicit watch, so that we know that the remote deployment fails.
* This short term solution is to let RemoteDeploymentWatcher always generate ChildTerminated,
  also for non-addressTerminated.
* It's possibly racy since ChildTerminated is not idempotent.
Send ChildTerminated before Terminated when AddressTerminated, see #2983

* Replaces the previous half-baked removeChildWhenToAddressTerminated