public static Function<? super RpcClient, MetricCollectingRpcClient> newDecorator(
            MeterIdPrefixFunction meterIdPrefixFunction) {
        requireNonNull(meterIdPrefixFunction, "meterIdPrefixFunction");
        return builder(meterIdPrefixFunction).newDecorator();
    }
Returns an {@link RpcClient} decorator that tracks request stats using {@link MeterRegistry}.
core/src/main/java/com/linecorp/armeria/client/metric/MetricCollectingRpcClient.java