[llvm] [Coro] Amortize debug info processing cost in CoroSplit (PR #109032)

[Adrian Prantl via llvm-commits]

adrian-prantl wrote:

> With https://github.com/llvm/llvm-project/pull/114537 out, there’s quite a bit of sequencing in the remaining 12 commits. I can combine some of the remaining commits into larger PRs if it makes the review logistics a bit easier.

On the contrary, 12 PRs with a trivial NFC refactor will be easier to review than 1 large one.

https://github.com/llvm/llvm-project/pull/109032