Rewrite chunking to work with intents.

This slows down chunking significantly for bots in a large number of
guilds since it goes down from 75 guilds/request to 1 guild/request.
However the logic was rewritten to fire the chunking request
immediately after receiving the GUILD_CREATE rather than waiting for
all the guilds in the ready stream before doing it.

discord/gateway.py

@@ -370,7 +370,7 @@ class DiscordWebSocket:
             }
 
         if state._intents is not None:
-            payload['d']['intents'] = state._intents
+            payload['d']['intents'] = state._intents.value
 
         await self.call_hooks('before_identify', self.shard_id, initial=self._initial_identify)
         await self.send_as_json(payload)