Reland "Update Glanceable Hub's AppWidgetHostListener impl for widget events"

This change updates GlanceableHub's custom AppWidgetHostListener
implementation to add support for the new collectWidgetEvents method.
This enables event reporting for the hub's widgets.

The reland also updates AppWidgetHost to run collectWidgetEvents on the
main thread.

Bug: 364655296
Test: Manual, use widgets on mobile hub and confirm that they are
 reported
Test: GlanceableHubWidgetManagerServiceTest
Test: Launcher3Tests:BindWidgetTest
Flag: android.appwidget.flags.engagement_metrics
Change-Id: I2ee816009ef82f1cc021c1c51dcdf06540dae93f