Update cmake to find_package(CUDAToolkit)

[frobnitzem]

The current CMakeLists.txt uses both enable_language(CUDA) and find_package(CUDA). The latter is deprecated in favor of FindCUDAToolkit, introduced in cmake 3.17.

A straightforward fix would be to add
find_package(CUDAToolkit)
target_link_libraries(cuda::toolkit INTERFACE CUDA::cublas ...)

but CUB still has to be added manually, and the device-specific compile options should be re-visited too.