[llvm] [DirectX] Error handling improve in root signature metadata Parser (PR #149232)

[Chris B via llvm-commits]

https://github.com/llvm-beanz commented:

Some high level feedback. In general we should try to avoid taking ownership and copying around strings. Since most common uses of strings in LLVM are either static constants or associated with data owned by the module you can usually use StringRef over std::string.

Overall I think this is the right direction.

https://github.com/llvm/llvm-project/pull/149232