Enable count-unrealized by default (#3389)

## Issue Addressed

Enable https://github.com/sigp/lighthouse/pull/3322 by default on all networks.

The feature can be opted out of using `--count-unrealized=false` (the CLI flag is updated to take a parameter).

lighthouse/tests/beacon_node.rs

@@ -132,6 +132,37 @@ fn fork_choice_before_proposal_timeout_zero() {
         .with_config(|config| assert_eq!(config.chain.fork_choice_before_proposal_timeout_ms, 0));
 }
 
+#[test]
+fn count_unrealized_default() {
+    CommandLineTest::new()
+        .run_with_zero_port()
+        .with_config(|config| assert!(config.chain.count_unrealized));
+}
+
+#[test]
+fn count_unrealized_no_arg() {
+    CommandLineTest::new()
+        .flag("count-unrealized", None)
+        .run_with_zero_port()
+        .with_config(|config| assert!(config.chain.count_unrealized));
+}
+
+#[test]
+fn count_unrealized_false() {
+    CommandLineTest::new()
+        .flag("count-unrealized", Some("false"))
+        .run_with_zero_port()
+        .with_config(|config| assert!(!config.chain.count_unrealized));
+}
+
+#[test]
+fn count_unrealized_true() {
+    CommandLineTest::new()
+        .flag("count-unrealized", Some("true"))
+        .run_with_zero_port()
+        .with_config(|config| assert!(config.chain.count_unrealized));
+}
+
 #[test]
 fn freezer_dir_flag() {
     let dir = TempDir::new().expect("Unable to create temporary directory");