The function `direction_to_<some projection model>` computes the inverse of `<some projection model>_to_direction`.
Some of these functions had a bug where they mirror the x-axis, and some of them could be simplified.
I added round-trip tests for all of them.
This MR might change the behavior of the renderer when using equiangular_cubemap_face_to_direction:
I normalized the result vector. I looked at the usages and I think it's normalized later anyways, but someone else should probably verify that this doesn't cause issues.
Pull Request: https://projects.blender.org/blender/blender/pulls/123932
717c970297