Implement the SSH session to call protocol bridge:
- Add FrameFramedReader/FrameFramedWriter for async I/O of length-prefixed EventEnvelope frames
- SshSession::recv() reads InterfaceEvent frames from the alknet-control:0 channel via mpsc
- SshSession::send() writes EventEnvelope frames to the alknet-control:0 channel via mpsc
- Add ControlChannelBridge implementing ControlChannelHandler for routing channel data
- SshHandler::channel_open_direct_tcpip routes alknet-control:0 to the bridge task
- Session Identity attached to every InterfaceEvent produced by recv()
- ControlChannelRouter gains take_handler() for non-control alknet-* channel routing
glm-5.1
30f2910567