Delete ReactNativeStack 🎉 🎉 🎉 (#10511)

* Removed createReactNativeComponentClassStack and renamed createReactNativeComponentClassFiber => createReactNativeComponentClass

* Removed findNumericNodeHandleStack and renamed findNumericNodeHandleFiber => findNumericNodeHandle

* Renamed ReactNativeFiberEntry => ReactNativeEntry

* Removed all references to ReactNativeFeatureFlags and RN stack

* Removed severl RN modules that are no longer used

* Renamed ReactNativeEntry => ReactNativeFiberEntry for now. We'll probably remove 'fiber' references later

* Update build results json

* Deleted snapshot

* Re-add accidentally deleted test

* Remove now-unnecessary hack in test

* Fix lint

* RN findNodeHandle no longer adds props directly to read-only owner (#10520)

* Added ReactNativeMount-test snapshot for 'renders and reorders children' test

src/node_modules/react-native/index.js

@@ -6,9 +6,4 @@
 
 'use strict';
 
-var ReactNativeFeatureFlags = require('ReactNativeFeatureFlags');
-var useFiber = ReactNativeFeatureFlags.useFiber;
-
-module.exports = useFiber
-  ? require('ReactNativeFiberEntry')
-  : require('ReactNativeStackEntry');
+module.exports = require('ReactNativeFiberEntry');