WP-CLI: Add "wp cavalcade job delete"

On our install, sometimes we see the same job for the same hook being duplicated multiple times with the same `nextrun` timestamp.

Regardless of my example, instead of using a SQL query to delete a job or multiple jobs, it would be handy if there was a wp-cli command that allowed us to remove said jobs.

If this sounds like a good idea, I recommend `wp cavalcade job delete` for this new subcommand, but that means a `wp cavalcade job` command should be created as this currently doesn't exist.

What do you think?