[Dual Shade] Fix missing padding above the shade on some wide screens.

For some unknown reason, on certain devices the top padding returned by
`WindowInsets.systemBarsIgnoringVisibility` is 0, even though the status
bar height is a positive value. This CL adds a separate check for status
bar height to compensate for this.

Fix: 391380435
Bug: 412969642
Test: Tested manually by opening the shade on an unfolded device where
 padding top was previously not applied.
Test: Unit tests still pass.
Flag: com.android.systemui.scene_container
Change-Id: I201742af36fb4af1c8db5737df0c5e7fae07f256