Add support for implied options

[Radiergummi]

In some cases, commands have options that imply other options, say:

  -m, --metrics           - Enable the metrics collector.
      --metrics-endpoint  - Endpoint to serve metrics on.
                            Implies --metrics. Default value: "/metrics".

If a metrics endpoint is given, the metrics feature is implied to be enabled as well. This should be configurable via a new option implies?: string[] that nicely complements depends and conflicts:

  .option("-m, --metrics", "Enable the metrics collector.")
  .option(
    "--metrics-endpoint",
    "Endpoint to serve metrics on.",
    {
      default: "/metrics",
      implies: ["metrics"]
    }
  )