[llvm] [clang] [AMDGPU] Adding the amdgpu-num-work-groups function attribute (PR #79035)

[Jun Wang via cfe-commits]

jwanggit86 wrote:

@krzysz00 Are you asking for something like the following:

```
"amdgpu-min-num-work-groups"="1,2,3", "amdgpu-max-num-work-groups"="4,5,6"
```
When both are given, min must be <= max.

https://github.com/llvm/llvm-project/pull/79035