[clang] [Clang][HIP][CUDA] Add `__cluster_dims__` and `__no_cluster__` attribute (PR #156686)

[Shilei Tian via cfe-commits]

shiltian wrote:

But why do others, such as `CUDAGlobal`, still have `__` in `Declspec`? It indeed doesn't have it for `GNU`.

https://github.com/llvm/llvm-project/pull/156686