[Dual Shade] Refactor lockscreen viewmodels + fix placement of notifs.

This CL primarily achieves 3 things:

* Replaces state flows in lockscreen view-models to be hydrated states.

* Fixes the positioning of the notifications stack on the lock screen to
  be below the small clock (for Dual Shade wide layout).

* Removes a few unnecessary references to `isShadeLayoutWide`.

Bug: 395060439
Test: Manually tested by observing notification placement on lockscreen
 in both small and large clock configuration.
Test: Added and updated unit tests.
Test: Existing unit tests still pass.
Flag: com.android.systemui.scene_container
Change-Id: Id4b874797d924dae98637ae7d4c0f0719aa603f2