ns-render with depth colormap support

[ethanweber]

This adds the ability to use a depth colormap and specify the min and max depth values to consider (optionally). I also move rendered_output_names to the BaseRender config.

[ethanweber]

Here are 3 different results using different near and far planes for depth colormapping. I'm using the poster scene.

ns-render ... --rendered_output_names rgb depth --downscale_factor 4
https://github.com/nerfstudio-project/nerfstudio/assets/16965789/a067131f-9bad-48d3-a5f3-4650700a134a

ns-render ... --rendered_output_names rgb depth --downscale_factor 4 --depth_near_plane 0.25 --depth_far_plane 2.0
https://github.com/nerfstudio-project/nerfstudio/assets/16965789/d2ee3ccd-141a-4cfd-bbb0-9c12f9d2b31c

ns-render ... --rendered_output_names rgb depth --downscale_factor 4 --depth_near_plane 1.5 --depth_far_plane 2.0
https://github.com/nerfstudio-project/nerfstudio/assets/16965789/ab012eac-e52d-4f41-acc8-f93cf551e509