RN: Cleanup ViewConfig Types

Summary:
Cleans up the Flow types for React Native ViewConfig. After this diff, we will have two new canonical types:

- `ViewConfig` which is what we get from native and what is registered in the `ReactNativeViewConfigRegistry`.
- `PartialViewConfig` which is what we generate statically and augment at runtime before registering with the `ReactNativeViewConfigRegistry`.

Changelog:
[Internal]

Reviewed By: JoshuaGross

Differential Revision: D25075299

fbshipit-source-id: 4b53927b2db437b615447b711e83db355d0cfa55

Libraries/Components/Picker/AndroidDialogPickerViewConfig.js

@@ -10,7 +10,7 @@
 
 'use strict';
 
-import type {GeneratedViewConfig} from '../../Utilities/registerGeneratedViewConfig';
+import type {PartialViewConfig} from 'react-native/Libraries/Renderer/shims/ReactNativeTypes';
 
 const AndroidDialogPickerViewConfig = {
   uiViewClassName: 'AndroidDialogPicker',
@@ -27,4 +27,4 @@ const AndroidDialogPickerViewConfig = {
   },
 };
 
-module.exports = (AndroidDialogPickerViewConfig: GeneratedViewConfig);
+module.exports = (AndroidDialogPickerViewConfig: PartialViewConfig);