[V3 RPC] Initial RPC library switch (#1634)

* Initial RPC library switch

* Use weak refs to the methods so cog unload works

* Add docs

* Black fixes

* Add jsonrpcserver to Pipfile.lock

redbot/__main__.py

@@ -160,7 +160,7 @@ def main():
         sentry_log.critical("Fatal Exception", exc_info=e)
         loop.run_until_complete(red.logout())
     finally:
-        rpc.clean_up()
+        red.rpc.close()
         if cleanup_tasks:
             pending = asyncio.Task.all_tasks(loop=red.loop)
             gathered = asyncio.gather(*pending, loop=red.loop, return_exceptions=True)