Update to latest libp2p (#1810)

## Description

Updates to the latest libp2p and includes gossipsub updates. 

Of particular note is the limitation of a single topic per gossipsub message.

Co-authored-by: blacktemplar <blacktemplar@a1.net>

beacon_node/network/src/nat.rs

@@ -4,7 +4,7 @@
 //! - UPnP
 
 use crate::{NetworkConfig, NetworkMessage};
-use get_if_addrs::get_if_addrs;
+use if_addrs::get_if_addrs;
 use slog::{debug, info, warn};
 use std::net::{IpAddr, SocketAddr, SocketAddrV4};
 use tokio::sync::mpsc;

beacon_node/network/src/service.rs

@@ -428,7 +428,6 @@ fn spawn_service<T: BeaconChainTypes>(
                                 id,
                                 source,
                                 message,
-                                ..
                             } => {
                                 // Update prometheus metrics.
                                 expose_receive_metrics(&message);