Function kitsune_p2p_types::auto_stream_select

pub fn auto_stream_select<LeftType, RightType, LSt, RSt>(
    left: LSt, 
    right: RSt
) -> impl Stream<Item = AutoStreamSelect<LeftType, RightType>> where
    LSt: Stream<Item = LeftType> + Unpin,
    RSt: Stream<Item = RightType> + Unpin, 

Merge two sub-streams so they can be polled in parallel, but still know when each individually ends, unlike futures::stream::select()