[llvm] [HLSL] Add descriptor table metadata parsing (PR #142492)

[Alex Sepkowski via llvm-commits]

alsepkow wrote:

>   return !(RegisterSpace >= 0xFFFFFFF0 && RegisterSpace <= 0xFFFFFFFF);

nit: I suggest naming to constants for improved readability. It is pretty easy to infer in this case but I think its a good habit. Up to you though.

---
Refers to: llvm/lib/Target/DirectX/DXILRootSignature.cpp:326 in 72ca44b. [](commit_id = 72ca44bc667aa0b8ad4488603d92513806fc4c46, deletion_comment = False)

https://github.com/llvm/llvm-project/pull/142492