Use events API to eager send attestations (#7892)

Co-Authored-By: hopinheimer <knmanas6@gmail.com>

Co-Authored-By: hopinheimer <48147533+hopinheimer@users.noreply.github.com>

Co-Authored-By: Eitan Seri-Levi <eserilev@ucsc.edu>

Co-Authored-By: Michael Sproul <michael@sigmaprime.io>

Co-Authored-By: Michael Sproul <michaelsproul@users.noreply.github.com>

lighthouse/tests/validator_client.rs

@@ -758,3 +758,21 @@ fn validator_proposer_nodes() {
             );
         });
 }
+
+// Head monitor is enabled by default.
+#[test]
+fn head_monitor_default() {
+    CommandLineTest::new().run().with_config(|config| {
+        assert!(config.enable_beacon_head_monitor);
+    });
+}
+
+#[test]
+fn head_monitor_disabled() {
+    CommandLineTest::new()
+        .flag("disable-beacon-head-monitor", None)
+        .run()
+        .with_config(|config| {
+            assert!(!config.enable_beacon_head_monitor);
+        });
+}