Scaling support for Gaussian Splats

[keyboardspecialist]

Feature

Currently, the vertex shader explicitly strips the scaling component from the view matrix. This was done for earlier work with meshopt. When quantizing positions we introduced a scaling factor in the glTF transform matrix. This would then get incorrectly applied to the splats when projecting into 2D space. With SPZ, we no longer have this scale. By not stripping this out, we scale as expected when applied to the modelMatrix. However, we don't want introduced regressions for any assets that apply a scale in the glTF or tileset json.