[llvm] [DebugInfo][RemoveDIs] Use iterators to insert everywhere (PR #102003)

[Jeremy Morse via llvm-commits]

jmorse wrote:

IT's this hunk: https://github.com/llvm/llvm-project/commit/1e05c3a93d8b0532f434619c00782ac1a6f2b69c

That produces most of the slowdown, 0.05% total. Not sure there's really anything to do about it.

I believe I originally promised this would all pay for itself when we removed all the branching / skipping of debug intrinsics in various passes, but we're not at the point of actually stripping those out yet.

https://github.com/llvm/llvm-project/pull/102003