Profiling/pretty printer

[johanfylling]

Adding a metrics pretty-printer replicating the opa eval --metrics --format pretty output

Engine engine = new Engine.Builder()
    .withBundleLoader(new TarballBundleLoader("authz",
        Path.of("bundles/authz.tar.gz")))
    .build();

SimpleMetrics metrics = new SimpleMetrics();

Engine.PreparedQuery pq = engine.prepareForEvaluation()
    .withMetrics(metrics)
    .build();

boolean allowed = query.eval(input, Boolean.class);

System.out.println(MetricsPrinter.metricsToString(metrics));

[sspaink]

Maybe mention this new requirement in the readme?