scope and interactions with co-routines

[JeffGarland]

We need to explore the design space w.r.t. scope and co-routines. This was pointed out to me as a potential issue by a committee member in Hagenberg. The two proposals were in-flight at the same time and it's not clear the interactions were considered.

I've created an initial example of some coroutine logic (mostly boilerplate) and experimental together. The more interesting cases are if there's some impact on the co_await and co_return logic. I'm out of time to play with this now so if someone wants to explore more examples that would be great.

https://godbolt.org/z/4KhqfrxGj