go/control: Add runtime provisioner type to host status output

[abukosek]

This PR adds the runtime provisioner type to the status output.

[peternose]

{
  "runtimes": {
    "8000000000000000000000000000000000000000000000000000000000000000": {
      "provisioner": "sandbox"
    }
  },
}

👍

[peternose]

		switch {
		case err != nil:
			n.logger.Error("failed to fetch host configuration",
				"err", err,
			)
		case provisioner != nil:
			status.Provisioner = provisioner.Name()
		default:
			status.Provisioner = "none"
		}

Could also use an empty string, as the comment says this is the name of the provisioner.

[abukosek]

I think "none" is a bit more user-friendly in this case :)