List<ClusterState> getSystemStatesReceived() {
        synchronized(timer) {
            return clusterStateBundles.stream()
                    .map(ClusterStateBundle::getBaselineClusterState)
                    .toList();
        }
    }
Returns the latest system state version received, or empty if none are received yet.
clustercontroller-core/src/test/java/com/yahoo/vespa/clustercontroller/core/DummyVdsNode.java