[SB][Call] Add test helpers for setting call state based on chips flag.

If ChipsModernization flag is off, then call state is managed via
OngoingCallRepository. But if the flag is on, then call state is managed
via ActiveNotificationsInteractor. This CL adds some test helpers that
sets the right call state depending on the flag's status.

This CL only updates OngoingCallInteractorTest, other tests will be
updated in future CLs.

Bug: 372657935
Flag: com.android.systemui.status_bar_chips_modernization
Test: atest OngoingCallInteractorTest
Change-Id: I5ef2c458a867770126da2708c0d0c59d8350c2e8