Extended Gossipsub metrics (#1577)

## Issue Addressed

N/A

## Proposed Changes

Adds extended metrics to get a better idea of what is happening at the gossipsub layer of lighthouse. This provides information about mesh statistics per topics, subscriptions and peer scores. 

## Additional Info

beacon_node/eth2_libp2p/src/peer_manager/client.rs

@@ -20,7 +20,7 @@ pub struct Client {
     pub agent_string: Option<String>,
 }
 
-#[derive(Clone, Debug, Serialize)]
+#[derive(Clone, Debug, Serialize, PartialEq)]
 pub enum ClientKind {
     /// A lighthouse node (the best kind).
     Lighthouse,
@@ -98,6 +98,12 @@ impl std::fmt::Display for Client {
     }
 }
 
+impl std::fmt::Display for ClientKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{:?}", self)
+    }
+}
+
 // helper function to identify clients from their agent_version. Returns the client
 // kind and it's associated version and the OS kind.
 fn client_from_agent_version(agent_version: &str) -> (ClientKind, String, String) {