Leverage lightgaussian for 15 times smaller PLY files

[LifeIsStrange]

lightgaussian has a very small effect on quality (PSNR) and reduce size by 15 times, which btw improve FPS
https://github.com/VITA-Group/LightGaussian
it is made of 3 components

1. gaussian pruning
2. SH distilation
3. vecquantization informed on gaussian importance weights from 1) + octree losless compression on position data and FP16

gaussian pruning is the only component with code released for now
both 1 and 2 are unique in that they selectively remove gaussians and SH with almost no loss of accuracy
most compression alternatives online act on step 3, as mostly non selective compression on attributes
the process though can be further optimized on the 40% unquantized gaussians if we follow aras-p blog https://aras-p.info/blog/2023/09/13/Making-Gaussian-Splats-smaller/
via BC7 partitioning and k-means on SH for truly SOTA compression but this is a digression as no one has combined both solutions ATM