Remove layer mask from public API.

Instead, use materials to determine the layer mask of an object.

This hides the details/complexities of how layers are used
to render different passes from the user and will allow the
renderer to do more advanced rendering passes.

PiperOrigin-RevId: 928682525
Change-Id: I1f53dc8d12d2e574de6528977f55e79f896c6e42

src/experimental/filament/compat/scene_geom_util.cc

@@ -268,7 +268,6 @@ UniquePtr<mjrfRenderable> CreateGeomRenderable(
     const mjtByte render_flags[mjNRNDFLAG]) {
   mjrfRenderableParams params;
   mjrf_defaultRenderableParams(&params);
-  params.layer_mask = geom.category;
   auto renderable = CreateRenderable(ctx, params);
   PrepareGeomMeshes(renderable.get(), geom, model_objs);
   UpdateGeomMaterial(renderable.get(), geom, model_objs, render_flags);