Messages: make 3-argument form of request() use "req"
Node, Demux: connect() takes contravariant Receiver
add SocketServer
add SafeCloseableTestBase, ExecutorTestBase and use in tests
Rescheduler: don't leak self reference from constructor of inner class
don't leak references to self in constructor
 - ActivityTimeout
 - BaseSsjpEndpoint
 - SocketServer