Framed Pipe

MPSC-based Pipe to read/write frames, somewhat like a message box over bytes

Example

```rust let (tx, mut rx) = framed_pipe(n * 2, 4);

let echo_data = vec![vec![0xFF; n], vec![1, 2], vec![], vec![0x0; n / 2]];
for _ in 0..100 {
    for data in echo_data.iter() {
        tx.clone().try_send(data).expect("send");
    }
    for data in echo_data.iter() {
        let rx_data = rx.next().await.unwrap().expect("rx");
        assert_eq!(&rx_data, data.as_slice());
    }
}

```