Add recvClose channel to stream

[dmcgowan]

Prevent panic from closing recv channel, which may be written to after close. Use a separate channel to signal recv has closed and check that channel on read and write.

Alternative to #139 for https://github.com/containerd/containerd/issues/8390

[dmcgowan]

Had to add additional

    select {
    case <-s.recvClose:
        return s.recvErr
    default:
    }

on receive to replace the err nil check. Since Go does not guarantee select order priority, messages could still be sent after a close was called, causing that test flake. If the receive and close happen at the same time, it isn't important which one wins.