[clang] [clang] Implement function pointer type discrimination (PR #96992)

[Daniil Kovalev via cfe-commits]

https://github.com/kovdan01 approved this pull request.

LGTM with minor mostly cosmetic comments. I'm OK with fixing them in a separate PR if it's too time-consuming now.

https://github.com/llvm/llvm-project/pull/96992