Fix T74939: Random Walk subsurface appearance in OptiX does not match other engines

Random Walk subsurface scattering did look different with OptiX because transmittance is
calculated based on the hit distance, but the OptiX implementation of `scene_intersect_local`
would return the distance in world space, while the Cycles BVH version returns it in object
space. This fixes the problem by simply skipping the object->world transforms in all the
places using the result of `scene_intersect_local` with OptiX.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D7232

Fix T74393: Cycles crashes when both OSL and Optix Denoising are enabled

Enabling viewport denoising causes Cycles to use a multi-device, which always returned NULL when
asked for OSL memory and would subsequently crash. This fixes that by returning the correct OSL
memory pointer from the CPU device in the special viewport denoising multi-device.

Cycles: Rework tile scheduling for denoising

This fixes denoising being delayed until after all rendering has finished. Instead, tile-based
denoising is now part of the "RENDER" task again, so that it is all in one task and does not
cause issues with dedicated task pools where tasks are serialized.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D6940

Fix CUDA out of memory error with OptiX viewport denoising on small GPUs

This makes the memory allocation for the denoiser state use the memory allocator in Cycles, which
will evict textures to host memory when there is not enough space on the device. This means the
allocation for the denoiser state won't just fail if there is no more space and instead more space is
made for it to work. Also simplifies code somewhat.

Cleanup: Remove superfluous "cuda_device_ptr" function

Cycles: Add option to change which sample to start viewport denoising at

This patch adds a new user-configurable option to change at which sample viewport
denoising should kick in. Setting it to zero retains previous behavior (start immediately), while
other values will defer denoising until the particular sample has been reached. Default is now
at one, to avoid the weirdness that is AI denoising at small resolutions.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D6906

Fix unnecessary Cycles OptiX kernel loading

With the OptiX viewport denoiser active, an OptiX device was added to the device list even when
rendering and denoising on different devices (e.g. CPU or CUDA) in background rendering. This
fixes it, so the OptiX device is only added when actually needed, as in only when OptiX denoising is
actually active in background rendering.

Cycles: Add support for adaptive kernel compilation to OptiX device

This modifies the common CUDA implementation for adaptive kernel compilation slightly to support both CUBIN and PTX output (the latter which is then used in the OptiX device). It also fixes adaptive kernel compilation on Windows.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D6851

Fix artifacts with Cycles viewport denoising when rendering with multiple CUDA devices

Rendering with multiple CUDA devices but denoising with OptiX caused parts of the image to go
missing at the start while the resolution was scaled. This is because the copy operation in
`MultiDevice::map_neighbor_tiles` which slices the copy across all devices would slice based on the
full resolution and not the scaled one and therefore copy incorrect data between devices.
Since this is not the recommended way of using viewport denoising anyway, simply avoid those
incorrect copies for now by disabling denoising while the resolution is scaled. Doing both rendering
and denoising with OptiX is not affected by this, since it avoids those copies altogether anyway.

Fix artifacts with Cycles viewport denoising when rendering with multiple CUDA devices

Rendering with multiple CUDA devices but denoising with OptiX caused parts of the image to go
missing at the start while the resolution was scaled. This is because the copy operation in
`MultiDevice::map_neighbor_tiles` which slices the copy across all devices would slice based on the
full resolution and not the scaled one and therefore copy incorrect data between devices.
Since this is not the recommended way of using viewport denoising anyway, simply avoid those
incorrect copies for now by disabling denoising while the resolution is scaled. Doing both rendering
and denoising with OptiX is not affected by this, since it avoids those copies altogether anyway.