Remove locks in PubsubNotifee

- Change `open_memory_channel(0)` to `open_memory_channel(math.inf)`, to
avoid `peer_queue.send` and `dead_peer_queue.send` blocking. This allows
us to remove the locks.
- Only catch `trio.BrokenResourceError`, which is caused by Pubsub when
it's closing.

libp2p/pubsub/pubsub.py

@@ -95,15 +95,15 @@ class Pubsub(Service, IPubsub):
         # Attach this new Pubsub object to the router
         self.router.attach(self)
 
-        peer_channels = trio.open_memory_channel[ID](0)
-        dead_peer_channels = trio.open_memory_channel[ID](0)
+        peer_send, peer_receive = trio.open_memory_channel[ID](math.inf)
+        dead_peer_send, dead_peer_receive = trio.open_memory_channel[ID](math.inf)
         # Only keep the receive channels in `Pubsub`.
         # Therefore, we can only close from the receive side.
-        self.peer_receive_channel = peer_channels[1]
-        self.dead_peer_receive_channel = dead_peer_channels[1]
+        self.peer_receive_channel = peer_receive
+        self.dead_peer_receive_channel = dead_peer_receive
         # Register a notifee
         self.host.get_network().register_notifee(
-            PubsubNotifee(peer_channels[0], dead_peer_channels[0])
+            PubsubNotifee(peer_send, dead_peer_send)
         )
 
         # Register stream handlers for each pubsub router protocol to handle