[llvm] [RemoveDIs] Add DPLabels support [3a/3] (PR #82633)

[Stephen Tozer via llvm-commits]

https://github.com/SLTozer commented:

Changes LGTM - just my most recent comment, and the outstanding question of `--try-experimental-debuginfo-iterators` left imo.

https://github.com/llvm/llvm-project/pull/82633