The main loop only handles transparent intersections from the camera ray.
Therefore we can simplify some things.
* Avoid PATH_RAY_CAMERA check, this is always true.
* Avoid path_state_next() call, we can just set transparent flag and increase transparent bounces. This way we avoid the function call and some branching.
Also remove debug num_ray_bounces++, this is incorrect here as no indirect bounce happens here.
Should be no functional changes.
Code there started becoming a bit too big, by splitting it up it'll make it
easier to do improvements or extending the features in there.
The layout is not totally final yet, would need to try de-duplicating parts
of code from split kernel with non-split integrators,
