Remove WindowInsets in TopAppBar

TopAppBar in edit mode was applying window insets even when the
Scaffold didn't expand to the top edge. Instead, set them to 0 and do
the same as for the other QS scenes (pass the known padding from the
viewmodel).

Test: manual, landscape, unfolded
Fixes: 396632343
Flag: com.android.systemui.qs_ui_refactor_compose_fragment
Change-Id: Ie025734c26be3f1613a6925884466578cc7a06aa