Caused by an integer overflow in the tiling utilities of OptiX SDK.

Seems for now it's easier to copy and modify code to our sources so
that we don't need to bump SDK version requirement (which might lead
to an increased driver requirement as well).

There are still some fixes needed from a newer driver to have such
denoising to work properly: Windows requires 511.79, Linux 510.54.

Thanks Patrick for investigation!