[Status Bar Refactor] Move a bunch of callbacks out of PanelBar and into

(N)PVC.

No need for the callbacks to flow through PanelBar when
(Notification)PanelViewController can just notify them directly.

Test: Manual (verify callbacks still trigger at the correct times)
Test: atest NotificationPanelViewControllerTest
Bug: 200063118
Change-Id: I374dc97a5fec8ce9c08b167dfb1112262b475f2a