Previously, vertex cache optimization was ran for the LOD meshes, but
was never ran for the base mesh or for the shadow meshes, including
shadow LOD chain (shadow LOD chain would sometimes get implicitly
optimized for vertex cache as a byproduct of base LOD optimization, but
not always). This could significantly affect the rendering performance
of geometry heavy scenes, especially for depth or shadow passes where
the fragment load is light.
Normal raycaster makes LOD generation process >2x slower and often
generates normals that look significantly worse compared to what the
simplifier comes up with by default. This was likely different before
last meshoptimizer upgrade, as the attribute metric was not functioning
properly, but now it looks like it's doing more harm than good.
This change makes it disabled by default but keeps an easy option to
re-enable it per mesh using LOD parameters for now until we get more
confidence and can remove the code outright.
Because the long term plan would be to disable this feature entirely,
the scripting API isn't changed, and it's just off-by-default there with
no way to re-enable.
