Add caching to Config::Info

The goal of this change is to make Config::Get(const Info<T>&)
fast so that we can use it in hot paths.

Source/Android/jni/NativeConfig.cpp

@@ -86,7 +86,7 @@ template <typename T>
 static void Set(jint layer, const Config::Location& location, T value)
 {
   GetLayer(layer, location)->Set(location, value);
-  Config::InvokeConfigChangedCallbacks();
+  Config::OnConfigChanged();
 }
 
 #ifdef __cplusplus