`points3D.bin` - Making EDGS easier to use with other 3DGS methods

[N-Demir]

What about exporting the dense point cloud as a points3D.bin file instead of in memory overriding the GaussianModel's splats? I think this would turn EDGS into an easier module that can be slotted into any 3DGS pipeline similar to bilagrid's success.

This suggestion is based on my understanding of the code that the key code implementing EDGS improvement on 3DGS is in init_gaussians_with_corr and after creating the dense point cloud the code uses it to initialize more gaussians and proceeds to training. This all happens in memory and so there's no intermediate output that could just be passed as an input to another 3DGS method. Most 3dgs methods will either use a random initialization or the sparse points3D.bin point cloud generated by colmap. If EDGS outputted points3D.bin it could be an easy addition to any other 3DGS method.

[yunhua-deng]

great suggestion, instead of using init_gaussians_with_corr() in the code level, outputting points3D.bin would be a much more convenient way of integration