[clang] Split -Wcast-function-type into a separate group (PR #86131)

[Abhin P Jose via cfe-commits]

Abhinkop wrote:

@AaronBallman @amy-kwan Here is the pull request for compiler-rt patch https://github.com/llvm/llvm-project/pull/86290. I am not able to add reviewers to that pull request.

https://github.com/llvm/llvm-project/pull/86131