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

[Felipe de Azevedo Piovezan via llvm-commits]

felipepiovezan wrote:

> Hi @artempyanykh, while I follow Adrian's suggestions, you could extract the first commit into a separate PR and we'll start reviewing/merging the NFC stuff one by one

The second commit can also be a PR on its own right now, it doesn't depend on the first one AFAICT, so we can review them in parallel 

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