SE-0388: Convenience Async[Throwing]Stream.makeStream methods

i think the main issue we would run into here is disambiguating what the link name would be relative to, because it may shadow a property of the same name in the current scope or one of the enclosing scopes.

for enclosing scopes we could always say the tuple label takes precedence, but i think it would be surprising (and doc-breaking) if tuple labels suddenly started shadowing references to things in the current scope.

Thank you all for your reviews and feedback. The language workgroup has decided to accept with modifications to use a tuple result type. More information is available in the announcement thread.