initiate new handshake after restart of receiving system, #20568

* we don't want to include the full origin address in each message,
  only the UID
* that means that the restarted receiving system can't initate a
  new handshake immediately when it sees message from unknown origin
* instead we inject HandshakeReq from the sending system once in a while
  (1 per second) which will trigger the new handshake
* any messages that arrives before the HandshakeReq are dropped, but
  that is fine since the system was just restarted anyway
* note that the injected handshake is only done for active connections,
  when a message is sent
* also changed the UID to a Long, but there are more places in old remoting
  that must be changed before we actually can use a Long value

fix lost first message, #20566

* the first message was sometimes dropped by the InboundHandshake stage
  because it came from unknown origin, i.e. the handshake had not completed
* that happended because the ordinary messagage arrived before the
  first HandshakeReq, which may happen since we sent the HandshakeReq
  over the control stream
* this changes so that HandshakeReq is sent over the same stream, not
  only on the control stream and thereby the HandshakeReq will arrive
  before any other message
* always send HandshakeReq as first message
  * also when the handshake on sender side has been completed at startup
  * moved code from preStart to onPull

akka-remote/src/main/scala/akka/remote/AddressUidExtension.scala

@@ -25,5 +25,12 @@ object AddressUidExtension extends ExtensionId[AddressUidExtension] with Extensi
 }
 
 class AddressUidExtension(val system: ExtendedActorSystem) extends Extension {
-  val addressUid: Int = ThreadLocalRandom.current.nextInt()
-}
+  val longAddressUid: Long = {
+    // FIXME we should use a long here, but then we need to change in Cluster and RemoteWatcher also
+    //ThreadLocalRandom.current.nextLong()
+    ThreadLocalRandom.current.nextInt()
+  }
+
+  @deprecated("Use longAddressUid instead", "2.4.x")
+  val addressUid: Int = longAddressUid.toInt
+}