Implement GBuffer prepass and deferred lighting (lights only).
This decouple lighting from the material shaders making them lighter,
less expensive and faster to compile.
Trying to keep a nice data flow so we could potentially use the
subpass programable blending feature on tiled GPU arch.
Not everything is covered yet and #105880 is making the GBuffer layout
a bit awkward and not easily extendable.
Pull Request: https://projects.blender.org/blender/blender/pulls/105868
335688dd42