This release backports a bug fix from 1.16.1

Fixes a soundness bug in io::Take (#4428). The unsoundness is exposed when leaking memory in the given AsyncRead implementation and then overwriting the supplied buffer:

impl AsyncRead for Buggy {
    fn poll_read(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        buf: &mut ReadBuf<'_>
    ) -> Poll<Result<()>> {
      let new_buf = vec![0; 5].leak();
      *buf = ReadBuf::new(new_buf);
      buf.put_slice(b"hello");
      Poll::Ready(Ok(()))
    }
}

Fixed

• io: soundness don't expose uninitialized memory when using io::Take in edge case (#4428)