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

[Jonas Devlieghere via llvm-commits]

JDevlieghere wrote:

> What sort of conflicts/breakages are you expecting? I guess API breaks on DIBuilder for custom frontends? Other things to look out for?

Just regular merge conflicts when we merge this into the Swift fork. This PR is upstreaming ptrauth support and started off based on the downstream code, but after a few iterations of review it looks a bit different. That's totally fine, as the result is better for it, but git will need a hand with the merge. The only reason I'm bringing it up is because last time this PR landed on a Friday afternoon (before it got revert) which left us little to deal with all this. 

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