Fix issue that widget picker is only half of screen in foldable.

Apply the extra top padding only if device is in portrait and aspect
 ratio is beyond 1.5 to keep the original intent of avoiding showing
 a single pane widget picker in super elongated form. In b/214215594,
 a top padding was applied for w720, but in fold, it ended up showing
 the picker only half way up. So, changed it to consider aspect ratio.

In b/315055849 the tablet portrait will use full width two pane picker,
and then, it will also not need this extra top padding. In that change,
we will use the flag to guard applying this extra padding.

See screen/cast/NTYwMjU1MzY4NDI5NTY4MHw3NDIxYzU0Mi1lNg

Test: WidgetPickerImageTest and Manual (screencast above)
Bug: 317013493
Flag: N/A
Change-Id: I90e0c416f0f05460960983588edf0068d99cd1a6