[llvm] [LLVM][NewPM] Add C API for running the pipeline on a single function. (PR #103773)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

Please also add this to the release notes. (Together with your previous change, I think I forgot about that one...)

https://github.com/llvm/llvm-project/pull/103773