[Breaking] Enable clustered lighting by default

[mvaligursky]

Until now, the clustered lighting was a feature the user had to opt in.
This PR makes it the default option, and the original lighting system is opt in.

If the original system needs to be used, this is the API to call:

            app.scene.clusteredLightingEnabled = false;

Note that by default, the area lights and cookie textures are disabled for clustered lighting (in order to keep the shader smaller / faster to compile), and can be enabled this way if needed:

            app.scene.lighting.cookiesEnabled = true;
            app.scene.lighting.areaLightsEnabled = true;