Use existing peer count metrics loop to check for open_nat toggle (#6800)

* implement update_nat_open function in network_behaviour for tracking incoming peers below a given threshold count

* implement update_nat_open function in network_behaviour for tracking incoming peers below a given threshold count

* tidy logic and comments

* move logic to existing metrics loop

* revert change to network_behaviour protocol check

* clippy

* clippy matches! macro

* pull nat_open check outside of peercounting loop

* missing close bracket

* make threshold const

beacon_node/lighthouse_network/src/peer_manager/peerdb/peer_info.rs

@@ -122,6 +122,24 @@ impl<E: EthSpec> PeerInfo<E> {
         self.connection_direction.as_ref()
     }
 
+    /// Returns true if this is an incoming ipv4 connection.
+    pub fn is_incoming_ipv4_connection(&self) -> bool {
+        self.seen_multiaddrs.iter().any(|multiaddr| {
+            multiaddr
+                .iter()
+                .any(|protocol| matches!(protocol, libp2p::core::multiaddr::Protocol::Ip4(_)))
+        })
+    }
+
+    /// Returns true if this is an incoming ipv6 connection.
+    pub fn is_incoming_ipv6_connection(&self) -> bool {
+        self.seen_multiaddrs.iter().any(|multiaddr| {
+            multiaddr
+                .iter()
+                .any(|protocol| matches!(protocol, libp2p::core::multiaddr::Protocol::Ip6(_)))
+        })
+    }
+
     /// Returns the sync status of the peer.
     pub fn sync_status(&self) -> &SyncStatus {
         &self.sync_status