Allow remotes to not open a legacy substream (#7075)

* Allow remotes to not open a legacy substream

* Misc fixes

* Special case first protocol as the one bearing the handshake

substrate/client/service/src/lib.rs

@@ -285,7 +285,6 @@ async fn build_network_future<
 							sc_rpc::system::PeerInfo {
 								peer_id: peer_id.to_base58(),
 								roles: format!("{:?}", p.roles),
-								protocol_version: p.protocol_version,
 								best_hash: p.best_hash,
 								best_number: p.best_number,
 							}