Override intern graph calls in flipper-ui-core

Summary:
> "Hi, kids, do you like violence?"

Alrighty, in flipper-frontend-core we have the **base** implmenetation of flipperLib (the thing exposed to the plugins). This base implementation is never used directly by the plugins, rather it is shared code used by the  real consumers - flipper-ui-core (regular Flipper with UI) and flipper-server-companion (the thing that allows hosting plugins on the server).
These real consumers actually run the plugins and expose flipperLib to the plugins.
In flipper-ui-core we have a more sophisticated logic of calling the intern graph - we check for VPN connection and authn. Therefore, to expose the same way of handling intern graph requests we **override** intern graph calls provided by flipper-frontend-core.
*Ideally*, we should move checking for VPN connection and authn to flipper-frontend-core, but currently it is a lot of effort for very little gains:
1. flipper-frontend-core does not have a notion of a user
2. Even if we move the authn-related logic there the only real consumer of that effort if flipper-server-companion that is used only by UIQR (which in its turn is barely used in the headless mode and do not require authn-related logic).

Thus, we just override intern graph request on the flipper-ui-core side since it is the simplest and the most impactful thing to do at the moment.

Reviewed By: LukeDefeo

Differential Revision: D49494922

fbshipit-source-id: 6f1d521af7ca5bd50549b7bc328d6b8fcab98389

desktop/flipper-ui-core/src/utils/flipperLibImplementation/index.tsx

@@ -17,7 +17,12 @@ import {addNotification} from '../../reducers/notifications';
 import {deconstructPluginKey} from 'flipper-common';
 import {RenderHost} from 'flipper-frontend-core';
 import {setMenuEntries} from '../../reducers/connections';
-import {currentUser, isConnected} from '../../fb-stubs/user';
+import {
+  currentUser,
+  internGraphGETAPIRequest,
+  internGraphPOSTAPIRequest,
+  isConnected,
+} from '../../fb-stubs/user';
 
 export function initializeFlipperLibImplementation(
   renderHost: RenderHost,
@@ -29,6 +34,8 @@ export function initializeFlipperLibImplementation(
     ...base,
     intern: {
       ...base.intern,
+      graphGet: internGraphGETAPIRequest,
+      graphPost: internGraphPOSTAPIRequest,
       currentUser,
       isConnected,
     },