[Sb refactor] Upgrade MobileIconsInteractorTest to use testScope

These tests were written before the library was available, and future
CLs will need the fine-grained time manipulation provided with
`TestScope`

Test: MobileIconsInteractorTest
Bug: 238425913
Change-Id: Ica20be32bc56f911625d5ed0e4bad90a046ebd30