Support Glanceable Hub widget configuration on HSUM

When a widget configuration intent is triggered on the headless system
user, retrieve an IntentSender through the
GlanceableHubWidgetManagerService and start the activity manually.
Previously this was done directly through the AppWidgetHost, but the
host resides on a different process in the foreground user on HSUM.

Test: atest WidgetConfigurationControllerTest
Test: atest GlanceableHubWidgetManagerServiceTest
Fix: 375036327
Flag: com.android.systemui.secondary_user_widget_host

Change-Id: Ifd10ebf78649a979f592360a0c0aa9d2b120b6c6