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

[Erich Keane via cfe-commits]

erichkeane wrote:

@lanza and @bcardosolopes are code owners here, so we need a +1 from one of you two.  I'll squash/merge for David after that happens (and when he/I are ready for it:) ).

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