Fix Nerfacto + Aria

[brentyi]

#2783 fixed an issue where the fisheye_crop_radius metadata field was being accidentally deleted. Unfortunately this also broke nerfacto support for Aria, since it exposed some broken fisheye sampling logic from #2617 (which was previously not being run).

Specific fixed problems:

• Sampled x/y coordinates were unnecessarily scaled by image_height // 2 and image_width // 2, since the crop radius is already in pixel units.
• The circle crop typically exceeds the bounds of the image, so sampling from the circle naively still has issues. We fix this with rejection sampling.

These changes + #2783 reduce artifacts.

Before:

aria-nerfstudio-render.mp4

After:

2024-02-22-21-27-52.mp4

[kerrj]

cool!