This PR adds world lighting to the irradiance cache and allows diffuse materials
to be lit by the world. The scene in the reference image is only lit by an environment
texture.
The reflection probe lib has been split into sampling the world probe and evaluating
the world probe. As evaluating the world probe requires to include more libraries and
data structures that aren't really needed for the irradiance cache shaders.
Pull Request: https://projects.blender.org/blender/blender/pulls/109516
91c3fd7a3b