Create a worker pool over the given Worker instances.
Dispatch is least-loaded: each operation goes to the worker with the fewest
in-flight tasks (ties resolve to the first). The count is bumped synchronously
at dispatch, so a burst of calls spreads across workers rather than piling
onto one. Under uniform op cost this degrades to round-robin.
Create a worker pool over the given Worker instances.
Dispatch is least-loaded: each operation goes to the worker with the fewest in-flight tasks (ties resolve to the first). The count is bumped synchronously at dispatch, so a burst of calls spreads across workers rather than piling onto one. Under uniform op cost this degrades to round-robin.