BEEFY: optimize voter event loop for fewer 'active' wakeups (#12760)

* client/beefy: remove high-freq network events from main loop

Network events are many and very frequent, remove the net-event-stream
from the main voter loop and drastically reduce BEEFY voter task
'wakeups'.

Instead have the `GossipValidator` track known peers as it already
has callbacks for that coming from `GossipEngine`.

Signed-off-by: acatangiu <adrian@parity.io>

substrate/client/beefy/src/communication/gossip.rs

@@ -139,6 +139,10 @@ impl<B> Validator<B> for GossipValidator<B>
 where
 	B: Block,
 {
+	fn peer_disconnected(&self, _context: &mut dyn ValidatorContext<B>, who: &PeerId) {
+		self.known_peers.lock().remove(who);
+	}
+
 	fn validate(
 		&self,
 		_context: &mut dyn ValidatorContext<B>,

substrate/client/beefy/src/communication/peers.rs

@@ -46,11 +46,6 @@ impl<B: Block> KnownPeers<B> {
 		Self { live: HashMap::new() }
 	}
 
-	/// Add new connected `peer`.
-	pub fn add_new(&mut self, peer: PeerId) {
-		self.live.entry(peer).or_default();
-	}
-
 	/// Note vote round number for `peer`.
 	pub fn note_vote_for(&mut self, peer: PeerId, round: NumberFor<B>) {
 		let data = self.live.entry(peer).or_default();
@@ -87,16 +82,13 @@ mod tests {
 		let mut peers = KnownPeers::<sc_network_test::Block>::new();
 		assert!(peers.live.is_empty());
 
-		// Alice and Bob new connected peers.
-		peers.add_new(alice);
-		peers.add_new(bob);
 		// 'Tracked' Bob seen voting for 5.
 		peers.note_vote_for(bob, 5);
 		// Previously unseen Charlie now seen voting for 10.
 		peers.note_vote_for(charlie, 10);
 
-		assert_eq!(peers.live.len(), 3);
-		assert!(peers.contains(&alice));
+		assert_eq!(peers.live.len(), 2);
+		assert!(!peers.contains(&alice));
 		assert!(peers.contains(&bob));
 		assert!(peers.contains(&charlie));