[Status Bar] Update wifi repository tests to use robolectric.

Other wifi pipeline tests don't pass by default on robolectric. Those
tests will be updated and added to robolectric in future CLs.

Bug: 291916037
Test: atest WifiRepositorySwitcherTest DisabledWifiRepositoryTest
WifiRepositoryImplTest
Test: atest SystemUiRoboTests

Change-Id: I7147a6415c2eb5a1451f2a9986eb25f726a13b67