Use host-driven visibility tracking instead of draw callbacks

The current callbacks do not trigger reliably after recent changes in
Launcher. This change updates the tracking to use new
start/stopVisibilityTracking APIs on AppWidgetHostView

Bug: 364655296
Test: CtsAppWidgetTestCases:WidgetEventsTest
Test: manual, test tracking when widget is covered by all apps or widget
 sheet
Flag: android.appwidget.flags.engagement_metrics

Change-Id: I9bd9b7b3829cbd1afb19a2600a1eb99eb05d75c0