Expand support for labeling dataproc jobs and clusters

[chrisvittal]

Both the gcloud dataproc clusters create and gcloud dataproc jobs submit commands can add --labels for tracking. It would be useful to handle these in hailctl more explicitly.

[jigold]

I agree this change would be great to have! I want to add monitoring to our projects to scrape the logs for any dataproc creation events and send a notification to Slack. Having the labels would help make the notification more informative.