Export NewAppScreen from the root (facebook#50801)

Summary:

New react native projects from react-native-communit/template use components from the `NewAppScreen` which is currently not root exported:

```
import {
  Colors,
  DebugInstructions,
  Header,
  LearnMoreLinks,
  ReloadInstructions,
} from 'react-native/Libraries/NewAppScreen';
```

This diff adds re-export of the NewAppScreen as a namespace to state the origin of imported components clearly.

Changelog:
[Internal]

Differential Revision: D73242541

Author: coado

packages/react-native/Libraries/__tests__/__snapshots__/public-api-test.js.snap

@@ -9082,6 +9082,7 @@ export type {
   VirtualizedSectionListProps,
 } from \\"./Libraries/Lists/VirtualizedSectionList\\";
 export { default as VirtualizedSectionList } from \\"./Libraries/Lists/VirtualizedSectionList\\";
+export * as NewAppScreen from \\"./Libraries/NewAppScreen\\";
 export { default as AccessibilityInfo } from \\"./Libraries/Components/AccessibilityInfo/AccessibilityInfo\\";
 export type {
   ActionSheetIOSOptions,

packages/react-native/index.js

@@ -238,6 +238,9 @@ module.exports = {
   get Networking() {
     return require('./Libraries/Network/RCTNetworking').default;
   },
+  get NewAppScreen() {
+    return require('./Libraries/NewAppScreen');
+  },
   get PanResponder() {
     return require('./Libraries/Interaction/PanResponder').default;
   },

packages/react-native/index.js.flow

@@ -318,6 +318,8 @@ export {default as NativeEventEmitter} from './Libraries/EventEmitter/NativeEven
 export {default as NativeModules} from './Libraries/BatchedBridge/NativeModules';
 export {default as Networking} from './Libraries/Network/RCTNetworking';
 
+export * as NewAppScreen from './Libraries/NewAppScreen';
+
 export type {
   PanResponderCallbacks,
   PanResponderGestureState,