Move logic to move the shade to the default display once locked to ShadeDisplaysRepository

+ MutableShadeDisplaysRepository deleted, it was not needed anymore after recent refactors
+ Moves logic to put the shade window back to the default display once locking the device to the repository (as opposed to StatusBarTouchShadeDisplayPolicy). This allows to have several policies sharing the same logic.
+ Introduce FakeShadeDisplayPolicy for testing

Bug: 362719719
Bug: 380444270
Test: ShadeDisplaysRepositoryTest, ShadePrimaryDisplayCommandTest, StatusBarTouchShadeDisplayPolicyTest
Flag: com.android.systemui.shade_window_goes_around
Change-Id: I6d108fbdac3060a5e6862634a5a1fc0bd4c14919