Summary:
This diff builds on top of the refactor to use `async/await` and adds multi-client support to Hot Module Reloading.
Thanks to async/await it's been quite straightforward to add this logic, since the only thing that I've had to do is to create a `Set` with the currently connected clients and passed the specified client to each method that was using the global client before.
This closes https://github.com/facebook/react-native/issues/14334
Reviewed By: davidaurelio
Differential Revision: D5611176
fbshipit-source-id: ec29438887342877c372b61132efada16af58fa5