Add builder header timeout flag (#5857)

* fix bitvector test random impl

* add a new flag that allows for configuring the timeout for get builder header api calls

* make cli

* add upper limit check, changes based on feedback

* update cli

* capitalization

* cli fix

lighthouse/tests/beacon_node.rs

@@ -636,6 +636,26 @@ fn builder_fallback_flags() {
     );
 }
 
+#[test]
+fn builder_get_header_timeout() {
+    run_payload_builder_flag_test_with_config(
+        "builder",
+        "http://meow.cats",
+        Some("builder-header-timeout"),
+        Some("1500"),
+        |config| {
+            assert_eq!(
+                config
+                    .execution_layer
+                    .as_ref()
+                    .unwrap()
+                    .builder_header_timeout,
+                Some(Duration::from_millis(1500))
+            );
+        },
+    );
+}
+
 #[test]
 fn builder_user_agent() {
     run_payload_builder_flag_test_with_config(