[llvm] [mlir] [Dwarf] Support `__ptrauth` qualifier in metadata nodes (PR #83862)

[Jonas Devlieghere via llvm-commits]

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

I would've probably done the inverse and shifted the `RawData` in the constructor, stored them as individual fields in a struct and have the getters operate on that. And of course have a new vector to return the raw data. But it looks like we rely on `RawData` more than on the getters, so this might be slightly more efficient. LGTM! 

https://github.com/llvm/llvm-project/pull/83862