Supervisor for core services. These are the services that need to start once Locator has determined the cluster state.

Nested services:

• Beethoven.Allocator Stack of services to track and aggregate signals to determine how busy a node is.
• Beethoven.HwMon Hardware monitor stack. Tracks hardware resource consumption and both stores the data historically and sends signals to Allocator.
• Beethoven.CoreServer Node monitoring service. Can send signals to callers when node state changes.
• Beethoven.BeaconServer TCP server for Beethoven instances to find each other. This interacts with the Locator service on other nodes.
• Beethoven.RoleMgmt Role management and allocation service that can host roles defined in config.ex.