[clang] [CIR] Call code gen; create empty cir.func op (PR #113483)

[Shoaib Meenai via cfe-commits]

smeenai wrote:

I created https://github.com/llvm/clangir/issues/1062 to track the location discussion in the incubator so that we can come back to it when the time is right.

https://github.com/llvm/llvm-project/pull/113483