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/tests/common/mod.rs

@@ -7,7 +7,7 @@ use eth2_libp2p::{GossipsubConfigBuilder, Libp2pEvent, NetworkConfig};
 use slog::{debug, error, o, Drain};
 use std::net::{TcpListener, UdpSocket};
 use std::time::Duration;
-use types::{EnrForkId, MinimalEthSpec};
+use types::{ChainSpec, EnrForkId, MinimalEthSpec};
 
 type E = MinimalEthSpec;
 use tempdir::TempDir;
@@ -105,10 +105,16 @@ pub async fn build_libp2p_instance(boot_nodes: Vec<Enr>, log: slog::Logger) -> L
         shutdown_tx,
     );
     Libp2pInstance(
-        LibP2PService::new(executor, &config, EnrForkId::default(), &log)
-            .await
-            .expect("should build libp2p instance")
-            .1,
+        LibP2PService::new(
+            executor,
+            &config,
+            EnrForkId::default(),
+            &log,
+            &ChainSpec::minimal(),
+        )
+        .await
+        .expect("should build libp2p instance")
+        .1,
         signal,
     )
 }