Inaccurate focal length estimates cause high training times

[PotatoPalooza]

If COLMAP does not properly estimate the camera's focal length in its intrinsic matrix estimation, this can drastically increase the training time of Nerf. Checks need to be added to ensure the focal length is within a reasonable range and to track the exact increase in time this issue causes. With basic testing, this issue seems to double the training time with inaccurate focal lengths.