ns-process-data: allow using best sparse model instead of always model 0

[luishresende]

COLMAP creates several models and tries to join them into a single model as I understand, if that does not work, the models will remain split.

I have however noticed that out of the x models, one of them is a good one, but nerfstudio is unable to pick it.

Can you check the COLMAP folder and see if you several models and import them into the COLMAP GUI interface and inspect them?

Then you can move the “good” model into sparse/0 and still run nerfstudio nerf.

I explained the issue here #3435

Originally posted by @abrahamezzeddine in #3357

I've been working with NeRFs and Gaussian Splatting for almost two years and have witnessed this issue several times in the Nerfstudio dataset pipeline (ns-process-data).