To keep backward compatibility, it looks for the new service (AutofillService),
then falls back to the old one (AutoFillService) if not found.
Bug: 35956626
Bug: 36024626
Test: manual verification with a custom service
Test: RunSettingsRoboTests passes
Change-Id: I64112ac5d796e94866e632ec8ea79a3fb13e3d9b