[clang] [Clang] Introduce scoped variants of GNU atomic functions (PR #72280)

[Artem Belevich via cfe-commits]

Artem-B wrote:

Just a FYI, that recent NVIDIA GPUs have introduced a concept of [thread block cluster](https://docs.nvidia.com/cuda/cuda-c-programming-guide/index.html#thread-block-clusters). We may need another level of granularity between the block and device.



https://github.com/llvm/llvm-project/pull/72280