Allow StreamMuxer to notify changes in the address (#1621)

* Allow StreamMuxer to notify changes in the address

* Fix doc link

* Revert accidental rename

* Other accidental rename

Co-authored-by: Roman Borschel <romanb@users.noreply.github.com>

core/src/network.rs

@@ -416,7 +416,14 @@ where
             Poll::Ready(PoolEvent::ConnectionEvent { connection, event }) => {
                 NetworkEvent::ConnectionEvent {
                     connection,
-                    event
+                    event,
+                }
+            }
+            Poll::Ready(PoolEvent::AddressChange { connection, new_endpoint, old_endpoint }) => {
+                NetworkEvent::AddressChange {
+                    connection,
+                    new_endpoint,
+                    old_endpoint,
                 }
             }
         };