Add __all__ attrs to async_stats and site_api modules

Author: ChrisLovering

botcore/async_stats.py

@@ -52,3 +52,6 @@ def _send(self, data: str) -> None:
     async def _async_send(self, data: str) -> None:
         """Send data to the statsd server using the async transport."""
         self._transport.sendto(data.encode('ascii'), self._addr)
+
+
+__all__ = ['AsyncStatsClient']

botcore/site_api.py

@@ -151,3 +151,6 @@ async def delete(self, endpoint: str, *, raise_for_status: bool = True, **kwargs
 
             await self.maybe_raise_for_status(resp, raise_for_status)
             return await resp.json()
+
+
+__all__ = ['APIClient', 'ResponseCodeError']