Debug widget restore issues in archiving mode

This CL includes following changes:
1. Include additional logging to reveal why getAppWidgetInfo() can
   return null value.
2. Explicitly asserts non-null value during assignment of
   appWidgetProviderInfo in debug environment to identify cases that
   leads to null value.

Bug: 336976070
Test: manual
Change-Id: I3f8c6ce628cae7b818f51f7a53fc005ba265136a