[llvm] [mlir] [mlir][EmitC] Add func, call and return operations and conversions (PR #79612)

[via llvm-commits]

AlexDenisov wrote:

@marbre thank you so much for working on this 🙌 

I just gave it a try and it's working great!

One minor suggestion: it would be nice to expose `populateFuncToEmitcPatterns` to combine it with other conversions without having to run a pass separately.




https://github.com/llvm/llvm-project/pull/79612