Add exec Node API to FlipperLib

Summary: Changelog: Allow flipper plugins to run "exec" Node API on Flipper server.

Reviewed By: mweststrate

Differential Revision: D32881149

fbshipit-source-id: 46486a47ee9824ca68897c19fd86b4afc7f8bf1d

desktop/flipper-plugin/src/__tests__/api.node.tsx

@@ -112,6 +112,7 @@ test('Correct top level API exposed', () => {
       "NormalizedMenuEntry",
       "Notification",
       "PluginClient",
+      "RemoteNodeAPI",
     ]
   `);
 });