Special trace for cron / cavalcade jobs

When a cavalcade job is running, we probably want to track it as a new service "$site_name-cavalcade" so metrics are not shared with web requests. We'd also want to change a lot of the metadata to be about the job being run. I can't find a way to actually hook before / after a cavalcade job is run though. Unless there's a special before / after WP CLI command hook - Cavalcade plugin doesn't provide any hooks for this.

This would possibly work at the Cavalcade-Runner level too, which is how we capture the data for CloudWatch, but this wouldn't let us get a xhprof trace of the job, or many other in-process data that we get for web requests.

@rmccue am I missing a way to be able to hook before a Cavalcade job is run? Aside from hook `all` and check `defined( 'CAVALCADE_JOB_ID' );` perhaps.