Remove the NetworkChan (#2577)

* Remove the NetworkChan from the API

* Remove the NetworkChan altogether

* Address review

* Fix line widths

* More line width fixes

* Remove pub visibility from entire world

* Fix tests

substrate/core/consensus/aura/src/lib.rs

@@ -964,6 +964,10 @@ mod tests {
 			}
 		}
 
+		fn uses_tokio(&self) -> bool {
+			true
+		}
+
 		fn peer(&self, i: usize) -> &Peer<Self::PeerData, DummySpecialization> {
 			&self.peers[i]
 		}