These changes don't affect behaviour at all, but are needed later.
- New approach of handling CPU kernel entry points (needed since the filter has a lot of kernels)
- Dedicated control over tile highlighting (needed to re-highlight tiles when they're being denoised)
- Renaming the PATH_TRACE task (it will handle both path tracing and denoising later)
- Device-only memory: Already used in the split kernel, now a separate class
- Several changes in the kernel to improve numerical stability and prevent NaNs