More organization changs to the manager / worker pool

[stevenengler]

These changes are to prepare for the rust migration of the Manager.

• Workers now add their local counters to the global counters --- Rather than having each worker add its counters to the manager through the global worker pool, each worker now adds its counters to the global counters and the manager then later reads from the global counters.
• Worker pool now accesses the controller, pid watcher, and config directly --- This is work towards making the controller/manager/scheduler/workerpool more composable and to limit parent references.