Blender Git Loki

Cycles X: Reduce OPtiX memory usage on multi-device

The idea is to allow OptiX denoiser to modify input render buffers
when it is known it will not conflict with the path tracer.

Can be extended to the CPU rendering and OptiX denoising, but this
will need some generic way of copying denoised passes only between
render buffers.

Differential Revision: https://developer.blender.org/D11865