See if removing the TransportsSenderActor is feasible

[flub]

transports.rs:

TODO: Can I just send the TransportsSender along in the NodeStateMessage::SendDatagram message?? That way you don't have to hook up the sender into the NodeMap!

This is an interesting refactor that would change the MagicSender::poll_send to clone the TransportsSender and send it to the EndpointStateActor for MultipathMappedAddr::Mixed. That way we could get rid of this actor in TransportsSenderActor.

Not 100% sure it's possible, but likely.