Replace min_worker and max_worker with num_workers

[MichaelClifford]

The current ClusterConfig() has a parameter for both min_worker and max_worker. These parameters are used by the Ray Cluster resource for auto-scaling. Currently, deploying Ray Clusters via Appwrapper does not support Ray auto-scaling. So, we don't actually need both of these parameters right now.

We should update the ClusterConfig() to only take one parameter for this: num_workers

[Maxusmusti]

Solved with #266