[SB][Chip] Add annotations to enable/disable ChipsModernization in test

I frequently find myself writing
`@EnableFlags(StatusBarChipsModernization.FLAG_NAME)` in a test without
remembering to also enable StatusBarRootModernization, which
ChipsModernization is dependent on. This can cause test failures like
b/396595475 which are non-obvious.

This CL marks StatusBarChipsModernization.FLAG_NAME as deprecated to
discourage people from using it directly in tests and instead adds two
test annotations that should be used instead:

 - @EnableChipsModernization enables both ChipsModernization &
   RootModernization
 - @DisableChipsModernization that disables just ChipsModernization

This CL updates some test classes to use the new annotations, other test
classes will be updated in the next CL.

Bug: 372657935
Bug: 396595475
Flag: com.android.systemui.status_bar_chips_modernization
Test: atest OngoingActivityChipsWithNotifsViewModelTest
Change-Id: Ibafc7055f8bdda9766d8ab9e831af56fbe8ab243