Refactor interop tests and factories

- Add `close` and `disconnect` in `Host`
- Add `close` and `close_peer` in `Network`
- Change `IListener.close` to async, to await for server's closing
- Add factories for security transports, and modify `HostFactory`

tests/pubsub/floodsub_integration_test_settings.py

@@ -3,10 +3,10 @@ import asyncio
 import pytest
 
 from tests.configs import LISTEN_MADDR
+from tests.factories import PubsubFactory
 from tests.utils import cleanup, connect
 
 from .configs import FLOODSUB_PROTOCOL_ID
-from .factories import PubsubFactory
 
 SUPPORTED_PROTOCOLS = [FLOODSUB_PROTOCOL_ID]