This allow splitting shadow and light evaluation.
This is the first step to deferred shadowing.
The evaluate closure types can be dynamically
set which mean we can have arbitrary BSDF
evaluation inside the same shader.
This also contain some refactor to `light_lib.glsl`
for more consistency and less clutter.
Note that this breaks the SSS translucency
as the shadow evaluation changes for these.
A new solution for this feature is to be found
Pull Request: https://projects.blender.org/blender/blender/pulls/113257
7c694c9d04