[Dual Shade] Render the shade header in QS based on the compose state.

This removes the QS container view-model's dependence on the
`isShadeLayoutWide` flow, which will soon be removed.

This has the nice side effect of simplifying the related code.

Bug: 354926927
Bug: 338033836
Test: Manually tested by opening and closing both shades on both a
 folded and unfolded device, verifying the shade header clock appears as
 expected.
Flag: com.android.systemui.scene_container
Change-Id: I743e9964e54ab1fa115b4602910bdd763fb69252