Add Datadog metric support and --version CLI flag Datadog Support: - Add Datadog and DogStatsD to METRIC_RECEIVERS - Properly differentiate factory-pattern (Prometheus) vs direct-action (StatsD/Datadog) clients - Support Datadog.increment, Datadog.gauge, Datadog.timing, etc. - Add distribution method support for histograms CLI --version flag: - Add --version option to print version and exit - Update help text to include --version Tests: - Add tests for Datadog.increment, DogStatsD.increment - Add tests for Datadog.gauge, Datadog.timing - Add tests for --version flag Documentation: - Update README with Datadog/DogStatsD in metrics table - Add --version to CLI options Co-authored-by: r.buddie <r.buddie@gmail.com>#10