Consider offering `try_next() -> Result<Option<T>>` for our stream-like things

[dbolduc]

Our stream-like things all have a next() (or maybe poll()) method which return an Option<Result<T>>.

So often example code looks like:

let mut stream = ...;
while let Some(item) = stream.next().await.transpose()? {
  println!("item={item:?}");
}

To slightly improve application ergonomics, we could consider offering a try_next() for our streams as a shorthand for omitting the transpose() (akin to futures::TryStreamExt)

let mut stream = ...;
while let Some(item) = stream.try_next().await? {
  println!("item={item:?}");
}