[llvm] [DebugInfo][RemoveDIs] Add local-utility plumbing for DPValues (PR #72276)

[Orlando Cazalet-Hyams via llvm-commits]

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

LGTM (there's one outstanding question I've "pinged" but I'm happy for that to be addressed, or not, when landing).

https://github.com/llvm/llvm-project/pull/72276