The function direction_to_fisheye_lens_polynomial computes the inverse of
fisheye_lens_polynomial_to_direction.
Previously the function worked almost correctly if all parameters except k_0
and k_1 were zero (in that case it was correct except for flipping the x-axis).
I replaced the fixed-point iteration (?) by Newton's method and implemented a
test to make sure it works correctly with a wider range of parameter sets.
Pull Request: https://projects.blender.org/blender/blender/pulls/123737
1b09654530