Track the amount of time task manager workers are occupied versus not

We should track how efficient the Task Manager workers are when it comes to running tasks. This will help us understand if we need to make improvements to task throughput by reducing the idle time each worker has by starting the next task.

Some of the following information may be useful to have:

Total time spent (in ms) where the workers were running tasks
Total time spent (in ms) where the workers were idle
Percentage of time spent running tasks

Note: We should implement the calculations independently from the poll interval. At collection time, we should include in in our calculation the tasks that are currently running (for their now - start time) and in the next collection the remaining time of the given task.

elastic / kibana

Track the amount of time task manager workers are occupied versus not #180635