1. Remove redundant total_workers_connected field which is same as size of worker
table.

2. total_worker_slots is deprecated in WQ stats and will reflect the number of
running tasks as default. total_workers_joined is similary deprecated and will
reflect size of worker table.

3. count of workers will reflect init + ready + active workers
Remove the worker states. Instead, use counts of known_workers which tracks all
workers that have identified themselves and available_workers that track workers
that with available resources. These are used in WQ stats, debugging, and places
where we need to know if workers are available for running a task.