Add inferfaceOnly option to CodegenSchema

Summary: In some cases the implementation for native modules are more advanced and we cannot currently generate some of the files. We've decided in these cases to only generate the props + events for now, so this flag `interfaceOnly` will only generate those files 👍

Reviewed By: TheSavior

Differential Revision: D14295980

fbshipit-source-id: 1790825143206a84469015e08958bf6f00ffde52

packages/react-native-codegen/src/generators/GenerateComponentDescriptorH.js

@@ -55,6 +55,9 @@ module.exports = {
 
         return Object.keys(components)
           .map(componentName => {
+            if (components[componentName].interfaceOnly === true) {
+              return;
+            }
             return componentTemplate.replace(/::_CLASSNAME_::/g, componentName);
           })
           .join('\n');