Function buffer_time_with 

pub fn buffer_time_with<T, S, SF, SFut>(
    ms: u64,
    s: S,
    sleep_fn: SF,
) -> impl Stream<Item = Vec<T>>
where
    S: Stream<Item = T> + Unpin,
    SF: Fn(Duration) -> SFut,
    SFut: Future<Output = ()> + Unpin,

Runtime-agnostic buffer_time with custom sleep function