[clang] [llvm] [HLSL] Implement SV_GroupThreadId semantic (PR #117781)

[Zhengxing li via llvm-commits]

lizhengxing wrote:

@sudonatalie
Hello Natalie,
Could you help review this PR when you're available since it will modify your changes (https://github.com/llvm/llvm-project/pull/82536), Thanks.

https://github.com/llvm/llvm-project/pull/117781