Refactor SharedNotificationContainerInteractor/ViewModel.

The change described below only affects the code enabled by the
`SceneContainer` flag.

`ConfigurationBasedDimensions` (the class and corresponding `Flow`) is
currently defined twice, once in `SharedNotificationContainerInteractor`
and once in `SharedNotificationContainerViewModel`. To simplify, we can
remove the former and keep the latter, since this code only deals with
presentation logic rather than business logic, making the domain-layer
version unnecessary.

This is part of a refactoring that will improve NSSL positioning to
support Dual Shade and Connected Displays.

Bug: 338033836
Flag: com.android.systemui.scene_container
Test: Verified manually by opening the shade on both folded and unfolded
 foldable device and observing that notifications are placed normally.
Test: Existing unit tests still pass.

Change-Id: Id6c138c29d7e4ec3743524e708f4b2e17dbe6da7