Experiments have shown that the OptiX denoiser performs best when operating on images that have their origin at the top-left corner, while Blender renders with the origin at the bottom-left corner. Simply flipping the image vertically before and after denoising is a relatively trivial operation, so this patch introduces this as an additional preprocessing and postprocessing step for denoising when the OptiX denoiser is used. Additionally, this patch also removes an unused helper function, now that OptiX 8.0 is the minimum. Pull Request: https://projects.blender.org/blender/blender/pulls/145358