Triage BaseController member visibility

[bitpshr]

The notify method is exposed publicly on the BaseController, but it should be protected. It's an anti-pattern for notification to be triggered externally since it should already be triggered on every supported state change.

We should also triage all member visibility on the BaseController.

[Gudahtt]

This is obsolete with the new controller design. We'll be auditing member visibility as we migrate each controller to the new API.