NSSL Migration - Animate top padding on shade pulldown

This to match existing behavior, with NSSL smoothly transitioning as
the user pulls down the shade and lets go. Do not animate when QS is
expanding, as that container controls the padding directly.

Flag: LEGACY MIGRATE_NSSL DISABLED
Fixes: 301238487
Test: atest SharedNotificationContainerViewModelTest
Change-Id: Ifecc7efbf7850ac9d4083070604fa6d292bfe2ba