private static List<NodeTimeseries> keep(List<NodeTimeseries> timeseries, Predicate<NodeMetricSnapshot> filter) {
        return timeseries.stream().map(nodeTimeseries -> nodeTimeseries.keep(filter)).toList();
    }
Returns the "peak load" in this: Which is for each load dimension,
the average of the highest reading for that dimension on each node.
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/autoscale/ClusterNodesTimeseries.java