Implement receiving messages from add-on on the client

Reviewed By: mweststrate

Differential Revision: D34249101

fbshipit-source-id: 07297b84ed8640e3b41599726ba613b6b4e2b62e

desktop/flipper-ui-core/src/devices/BaseDevice.tsx

@@ -390,5 +390,6 @@ export default class BaseDevice implements Device {
       instance.destroy();
     });
     this.sandyPluginStates.clear();
+    this.serverAddOnControls.unsubscribe();
   }
 }