Support native ViewManager inheritance on iOS

Summary:
**Motivation**
This is a re-worked version of #14260, by shergin's suggestion.

For iOS, if you want to inherit from a native ViewManagers, your custom ViewManager will not automatically export the parents' props. So the only way to do this today, is to basically copy/paste the parent ViewManager-file, and add your own custom logic.

With this PR, this is made more extensible by exporting the `baseModuleName` (i.e. the iOS `superclass` of the ViewManager), and then using that value to re-establish the inheritance relationship in `requireNativeComponent`.

**Test plan**
I've run this with a test project, and it works fine there. But needs more testing.

Opened this PR as [per shergin's suggestion](https://github.com/facebook/react-native/pull/10946#issuecomment-311860545) though, so we can discuss approach.

**Discussion**
* Android already supports inheritance, so this change should be compatible with that. But, not every prop available on `UIManager.RCTView.NativeProps` is actually exported by every ViewManager. So should `UIManager.RCTView.NativeProps` still be merged with `viewConfig.NativeProps`, even if the individual ViewManager does not export/use them to begin with?
* Does this break other platforms? [UWP](https://github.com/Microsoft/react-native-windows)?
Closes https://github.com/facebook/react-native/pull/14775

Differential Revision: D5392953

Pulled By: shergin

fbshipit-source-id: 5212da616acfba50cc285e2997d183cf8b2cd09f

Libraries/ReactNative/requireNativeComponent.js

@@ -70,13 +70,19 @@ function requireNativeComponent(
     viewConfig.propTypes = null;
   }
 
-  // The ViewConfig doesn't contain any props inherited from the view manager's
-  // superclass, so we manually merge in the RCTView ones. Other inheritance
-  // patterns are currenty not supported.
-  const nativeProps = {
-    ...UIManager.RCTView.NativeProps,
-    ...viewConfig.NativeProps,
-  };
+  let baseModuleName = viewConfig.baseModuleName;
+  let nativeProps = { ...viewConfig.NativeProps };
+  while (baseModuleName) {
+    const baseModule = UIManager[baseModuleName];
+    if (!baseModule) {
+      warning(false, 'Base module "%s" does not exist', baseModuleName);
+      baseModuleName = null;
+    } else {
+      nativeProps = { ...nativeProps, ...baseModule.NativeProps };
+      baseModuleName = baseModule.baseModuleName;
+    }
+  }
+
   for (const key in nativeProps) {
     let useAttribute = false;
     const attribute = {};