Misc Peer sync info adjustments (#1896)

## Issue Addressed
#1856 

## Proposed Changes
- For clarity, the router's processor now only decides if a peer is compatible and it disconnects it or sends it to sync accordingly. No logic here regarding how useful is the peer. 
- Update peer_sync_info's rules
- Add an `IrrelevantPeer` sync status to account for incompatible peers (maybe this should be "IncompatiblePeer" now that I think about it?) this state is update upon receiving an internal goodbye in the peer manager
- Misc code cleanups
- Reduce the need to create `StatusMessage`s (and thus, `Arc` accesses )
- Add missing calls to update the global sync state

The overall effect should be:
- More peers recognized as Behind, and less as Unknown
- Peers identified as incompatible

beacon_node/eth2_libp2p/src/peer_manager/mod.rs

@@ -147,7 +147,11 @@ impl<TSpec: EthSpec> PeerManager<TSpec> {
     pub fn goodbye_peer(&mut self, peer_id: &PeerId, reason: GoodbyeReason) {
         // get the peer info
         if let Some(info) = self.network_globals.peers.write().peer_info_mut(peer_id) {
-            debug!(self.log, "Sending goodbye to peer"; "peer_id" => peer_id.to_string(), "reason" => reason.to_string(), "score" => info.score().to_string());
+            debug!(self.log, "Sending goodbye to peer"; "peer_id" => %peer_id, "reason" => %reason, "score" => %info.score());
+            if matches!(reason, GoodbyeReason::IrrelevantNetwork) {
+                info.sync_status.update(PeerSyncStatus::IrrelevantPeer);
+            }
+
             // Goodbye's are fatal
             info.apply_peer_action_to_score(PeerAction::Fatal);
         }