Add events in Pubsub

To ensure `handle_peer_queue` and `handle_dead_peer_queue` are indeed
run before the tests finish. Previously, we get errors when performing
`iter_dag` after cancellation. This is because `handle_peer_queue` or
`handle_dead_peer_queue` is not actually run before the Service is
cancelled.

libp2p/tools/factories.py

@@ -245,6 +245,8 @@ class PubsubFactory(factory.Factory):
             strict_signing=strict_signing,
         )
         async with background_trio_service(pubsub):
+            await pubsub.event_handle_peer_queue_started.wait()
+            await pubsub.event_handle_dead_peer_queue_started.wait()
             yield pubsub
 
     @classmethod