WIP: Revamp CUDA support

[white238]

This removes the old deprecated FindCUDA and mimic's what @davidbeckingsale did for HIP support.

Breaking changes:

• cuda -> blt::cuda
• cuda_runtime -> blt::cuda_runtime
• CMAKE_LINK_WITH_NVCC -> BLT_CMAKE_LINK_WITH_NVCC (warning about former being deprecated)
• Removes Clang CUDA support (does anyone still use this @davidbeckingsale ?)

Thanks to @kennyweiss for sitting on a webex while I drastically rip support out from under myself!

[rhornung67]

@white238 will this require a syntax change for BLT users like the recent change in HIP support; e.g., 'cuda_runtime' --> 'cuda::runtime'?

[white238]

@white238 will this require a syntax change for BLT users like the recent change in HIP support; e.g., 'cuda_runtime' --> 'cuda::runtime'?

Yes this is a breaking change in the following ways:

cuda -> blt::cuda cuda_runtime -> blt::cuda_runtime CMAKE_LINK_WITH_NVCC -> BLT_CMAKE_LINK_WITH_NVCC

[white238]

We should probably add this to the blt::cuda target:

https://cmake.org/cmake/help/latest/module/FindCUDAToolkit.html#cuda-driver-library