[llvm] [RemoveDIs][DebugInfo] Add DPVAssign variant of DPValue (PR #77912)

[Jeremy Morse via llvm-commits]

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

LGTM, and all seems pretty reasonable. Presumably the refactoring / production of a class hierarchy is what @OCHyams is mangling right now?

https://github.com/llvm/llvm-project/pull/77912