Implement VoiceProtocol lower level hooks.

This allows changing the connect flow and taking control of it without
relying on internal events or tricks.

discord/guild.py

@@ -377,7 +377,7 @@ class Guild(Hashable):
 
     @property
     def voice_client(self):
-        """Optional[:class:`VoiceClient`]: Returns the :class:`VoiceClient` associated with this guild, if any."""
+        """Optional[:class:`VoiceProtocol`]: Returns the :class:`VoiceProtocol` associated with this guild, if any."""
         return self._state._get_voice_client(self.id)
 
     @property