[llvm] [Attributor] Pack out arguments into a struct (PR #119267)

[via llvm-commits]

elhewaty wrote:

> @arsenm, Thanks. Would you take a look? how to use `AAConvertOutArgumentFunction` It's not changing the sample function in the tests?

@shiltian can you take a look? 



https://github.com/llvm/llvm-project/pull/119267