Blender Git Loki

Cycles X: Move pass pixel processors to kernel_film

Currently no functional changes, just keep moving towards unifying
calculation logic between CPU and GPU.

There combined pass is equal in timing within a noise level, the
shadow catcher matte pass with approximated shadow is about 7%
faster (probably, due to difference in inline policy).

Differential Revision: https://developer.blender.org/D11478