Do not use Finch.async_request with Stream

[hissssst]

I can see that you've added Finch.async_request and doc even states this as a way to go to use it with Stream.resource, but

The biggest problem

It doesn't lazily read the data from socket on demand, it just sends whole response body into message queue which can just overflow the server. Any huge (let's say 1TB) response will just shut down any program using this approach. And people usually use Stream for these kind of problems (requesting huge files). So this is just misleading and has nothing to do with stream, please remove this from your documentation

[josevalim]

We should mention that async_request works as a firehose, it will immediately send messages as they come to the current process. I think discouraging its usage with Stream is fine. And we should mention Finch.stream as an option to lazily stream.