Reorganize CUDA compiler variants. (#2860)
Reorganize CUDA compiler variants. (#2860)

Features supported by newer CUDA versions and GPUs are usually a superset of the
features of the older GPUs. Using the most recent ones allows us to compile more
code.

* For NVCC, use the most recent GPU supported by particular CUDA version.
* For clang, pick the most recent supported CUDA version and GPU.
mattgodbolt/compiler-explorer,mattgodbolt/compiler-explorer,mattgodbolt/compiler-explorer,mattgodbolt/compiler-explorer,mattgodbolt/compiler-explorer,mattgodbolt/compiler-explorer,mattgodbolt/compiler-explorer,mattgodbolt/compiler-explorer