Update libp2p (#2101)

This is a little bit of a tip-of-the-iceberg PR. It houses a lot of code changes in the libp2p dependency. 

This needs a bit of thorough testing before merging. 

The primary code changes are:
- General libp2p dependency update
- Gossipsub refactor to shift compression into gossipsub providing performance improvements and improved API for handling compression



Co-authored-by: Paul Hauner <paul@paulhauner.com>

beacon_node/eth2_libp2p/tests/common/mod.rs

@@ -3,7 +3,8 @@ use eth2_libp2p::Enr;
 use eth2_libp2p::EnrExt;
 use eth2_libp2p::Multiaddr;
 use eth2_libp2p::Service as LibP2PService;
-use eth2_libp2p::{GossipsubConfigBuilder, Libp2pEvent, NetworkConfig};
+use eth2_libp2p::{Libp2pEvent, NetworkConfig};
+use libp2p::gossipsub::GossipsubConfigBuilder;
 use slog::{debug, error, o, Drain};
 use std::net::{TcpListener, UdpSocket};
 use std::sync::Weak;