Expose number of workers/executors per process

[glasnt]

Per conversation with @nhibberd just now

There's no mechanism (and no issue I can see) for showing how many workers/executors are on a box. If we want 40 workers, we want a mechanism to know how many workers are active.

From there, we can aggregate this data and then create alarms based on a lack of workers.

We need the data to start.