[llvm] [DirectX] Add Range Overlap validation (PR #152229)

[Justin Bogner via llvm-commits]

https://github.com/bogner approved this pull request.

Looks good. A couple of small comments left.

Before committing, could you make sure that the way we comment/document the root signatures in the tests are consistent? Most have the signature in a comment just before the `!dx.rootsignatures` metadata, but some like llvm/test/CodeGen/DirectX/rootsignature-validation-fail-root-descriptor-range.ll are missing the comment and llvm/test/CodeGen/DirectX/rootsignature-validation.ll has the comment but it's in a different spot in the file

https://github.com/llvm/llvm-project/pull/152229