swarm/: Allow disconnecting from Swarm and NetworkBehaviour (#2110)

Add `ExpandedSwarm::disconnect_peer_id` and
`NetworkBehaviourAction::CloseConnection` to close connections to a specific
peer via an `ExpandedSwarm` or `NetworkBehaviour`.

Co-authored-by: Max Inden <mail@max-inden.de>

swarm/src/test.rs

@@ -167,6 +167,8 @@ where
         self.inject_listener_closed = Vec::new();
         self.poll = 0;
     }
+
+    pub fn inner(&mut self) -> &mut TInner { &mut self.inner }
 }
 
 impl<TInner> NetworkBehaviour for CallTraceBehaviour<TInner>