Add basic metrics to libp2p

beacon_node/eth2-libp2p/src/metrics.rs

@@ -0,0 +1,16 @@
+pub use lighthouse_metrics::*;
+
+lazy_static! {
+    pub static ref ADDRESS_UPDATE_COUNT: Result<IntCounter> = try_create_int_counter(
+        "libp2p_address_update_count",
+        "Count of libp2p socked updated events (when our view of our IP address has changed)"
+    );
+    pub static ref PEER_CONNECT_COUNT: Result<IntCounter> = try_create_int_counter(
+        "libp2p_peer_connect_count",
+        "Count of libp2p peer connect events (not the current number of connected peers)"
+    );
+    pub static ref PEER_DISCONNECT_COUNT: Result<IntCounter> = try_create_int_counter(
+        "libp2p_peer_disconnect_count",
+        "Count of libp2p peer disconnect events"
+    );
+}