Currently our handshake requests do not include a version. This is
unfortunate as we cannot rely on the stream version since it is not the
sending node's version. Instead it is the minimum compatibility version.
The handshake request is currently empty and we do nothing with it. This
should allow us to add data to the request without breaking backwards
compatibility.
This commit adds the version to the handshake request. Additionally, it
allows "future data" to be added to the request. This allows nodes to craft
a version compatible response. And will properly handle additional data in
future handshake requests. The proper handling of "future data" is useful
as this is the only request where we do not know the other node's version.
Finally, it renames the TcpTransportHandshaker to
TransportHandshaker.
797f985067