[Garage Mode: Refactoring] Scoped out GarageModePolicy into separate
class.

Test: JUnit and Manual
Bug: 110113240
Change-Id: If74bf030dcef842eca1f8c0fa8e9758897be0cb9
(cherry picked from commit 06a666831768f85e042c49868e5ed27231ba95d7)
6 files changed