[clang] [clang][HLSL] Fix dangling StringRef in ParsedSemantic::Name (PR #200450)

[Justin Bogner via cfe-commits]

bogner wrote:

> Another option may be to change `std::string ParsedSemantic::Name` into a `const IdentifierInfo *Name`. That way we could save a string copy.

I think using IdentifierInfo would make more sense here. This both saves the copy and avoids arbitrary heap allocation.

> BTW, those [HLSL Tests / HLSL-Tests (hlsl-macos)](https://github.com/llvm/llvm-project/actions/runs/26661183723/job/78583815790?pr=200450) build errors seem unrelated to this PR's changes.

Yes, these look unrelated.

https://github.com/llvm/llvm-project/pull/200450