Create network_utils crate (#7761)

Anchor currently depends on `lighthouse_network` for a few types and utilities that live within. As we use our own libp2p behaviours, we actually do not use the core logic in that crate. This makes us transitively depend on a bunch of unneeded crates (even a whole separate libp2p if the versions mismatch!)


  Move things we require into it's own lightweight crate.


Co-Authored-By: Daniel Knopik <daniel@dknopik.de>

beacon_node/lighthouse_network/src/service/mod.rs

@@ -1,5 +1,4 @@
 use self::gossip_cache::GossipCache;
-use crate::EnrExt;
 use crate::Eth2Enr;
 use crate::config::{GossipsubConfigParams, NetworkLoad, gossipsub_config};
 use crate::discovery::{
@@ -33,6 +32,7 @@ use libp2p::swarm::{NetworkBehaviour, Swarm, SwarmEvent};
 use libp2p::upnp::tokio::Behaviour as Upnp;
 use libp2p::{PeerId, SwarmBuilder, identify};
 use logging::crit;
+use network_utils::enr_ext::EnrExt;
 use std::num::{NonZeroU8, NonZeroUsize};
 use std::path::PathBuf;
 use std::pin::Pin;