Improve peer performance for NAT'd nodes (#5345)

* Merge latest unstable

* Reduce diff

* Reduce logic, discover up to max peers

* Peer discovery for Natd peers

Author: AgeManning

beacon_node/lighthouse_network/src/peer_manager/mod.rs

@@ -880,8 +880,7 @@ impl<TSpec: EthSpec> PeerManager<TSpec> {
             let outbound_only_peer_count = self.network_globals.connected_outbound_only_peers();
             let wanted_peers = if peer_count < self.target_peers.saturating_sub(dialing_peers) {
                 // We need more peers in general.
-                // Note: The maximum discovery query is bounded by `Discovery`.
-                self.target_peers.saturating_sub(dialing_peers) - peer_count
+                self.max_peers().saturating_sub(dialing_peers) - peer_count
             } else if outbound_only_peer_count < self.min_outbound_only_peers()
                 && peer_count < self.max_outbound_dialing_peers()
             {