3-button mode tests close app tests

Tests now run in:
  - Portrait + 3 Button
  - Landscape + 3 Button
  - Portrait + Gestural
  - Landscape + Gestural

Moreover, the tests now share the code and assertions because they should behave exactly the same (except for the transition)

Test: atest FlickerTests
Bug: 167521849
Change-Id: Id88514d83e40c04bce3135cccdc142a2b2745597