Gossipsub scoring (#1668)

## Issue Addressed

#1606 

## Proposed Changes

Uses dynamic gossipsub scoring parameters depending on the number of active validators as specified in https://gist.github.com/blacktemplar/5c1862cb3f0e32a1a7fb0b25e79e6e2c.

## Additional Info

Although the parameters got tested on Medalla, extensive testing using simulations on larger networks is still to be done and we expect that we need to change the parameters, although this might only affect constants within the dynamic parameter framework.

beacon_node/eth2_libp2p/src/peer_manager/peer_info.rs

@@ -109,8 +109,8 @@ impl<T: EthSpec> PeerInfo<T> {
     }
 
     /// Returns score of the peer.
-    pub fn score(&self) -> Score {
-        self.score
+    pub fn score(&self) -> &Score {
+        &self.score
     }
 
     /// Returns the state of the peer based on the score.
@@ -132,6 +132,14 @@ impl<T: EthSpec> PeerInfo<T> {
         }
     }
 
+    pub(crate) fn update_gossipsub_score(&mut self, new_score: f64, ignore: bool) {
+        self.score.update_gossipsub_score(new_score, ignore);
+    }
+
+    pub fn is_good_gossipsub_peer(&self) -> bool {
+        self.score.is_good_gossipsub_peer()
+    }
+
     #[cfg(test)]
     /// Resets the peers score.
     pub fn reset_score(&mut self) {