implements AsyncIterable<T> for Lister<T>

[nleguen]

When needed to retrieve all streams or consumers instead of a paged list, this simple change makes possible to do something like:

for await(const info of jsm.streams.list()) {
  console.log(info.config.name); // do whatever you want with the info
}

It doesn't break the actual API: jsm.streams.list().next() still returns a list for the paged result.

[aricart]

LGTM

[aricart]

@nleguen thanks for the contribution

[aricart]

FIX #128