Make the return type of update_stream match with create_stream

[rauno56]

Makes the return type of update_stream on Context to match with create_stream. I can see how in the most common usecase, one would want to start using the updated stream immediately after - this change would save the network call of getting the stream after the update. Info is still reachable through cached_info().

PS. That's a breaking change. If you prefer to avoid it, I can rename it to get_or_update_stream that would match get_or_create_stream as well, but leave update_stream untouched.

[rauno56]

Any feedback on this, @Jarema?

[Jarema]

I will get back to this near the end of the week.