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

[Chris B via llvm-commits]

================
@@ -26,6 +28,80 @@ class Metadata;
 namespace hlsl {
 namespace rootsig {
 
+template <typename T>
+class RootSignatureValidationError
+    : public ErrorInfo<RootSignatureValidationError<T>> {
+public:
+  static char ID;
+  std::string ParamName;
----------------
llvm-beanz wrote:

```suggestion
  StringRef ParamName;
```

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