resolves elastic#98634

This adds a new object property to the event log kibana object named
task, with two properties to track the time the task was scheduled to
run, and the delay between when it was supposed to run and when it
actually started. This task property is only added to the appropriate
events.

	task: schema.maybe(
	  schema.object({
	    scheduled: ecsDate(),
	    schedule_delay: ecsNumber(),
	  })
	),