refactor: expose and use THandlerOutEvent type alias (#3368)

Previously, we used the full reference to the `OutEvent` of the `ConnectionHandler` in all implementations of `NetworkBehaviour`. Not only is this very verbose, it is also more brittle to changes. With the current implementation plan for #2824, we will be removing the `IntoConnectionHandler` abstraction. Using a type-alias to refer to the `OutEvent` makes the migration much easier.

protocols/rendezvous/src/client.rs

@@ -34,7 +34,7 @@ use libp2p_core::{Multiaddr, PeerId, PeerRecord};
 use libp2p_swarm::behaviour::FromSwarm;
 use libp2p_swarm::{
     CloseConnection, ConnectionId, ExternalAddresses, NetworkBehaviour, NetworkBehaviourAction,
-    NotifyHandler, PollParameters,
+    NotifyHandler, PollParameters, THandlerOutEvent,
 };
 use std::collections::{HashMap, VecDeque};
 use std::iter::FromIterator;
@@ -191,7 +191,7 @@ impl NetworkBehaviour for Behaviour {
         &mut self,
         peer_id: PeerId,
         connection_id: ConnectionId,
-        event: handler::OutboundOutEvent,
+        event: THandlerOutEvent<Self>,
     ) {
         let new_events = match event {
             handler::OutboundOutEvent::InboundEvent { message, .. } => void::unreachable(message),