Update glanceable hub layout specs on compact screens

This change enables flexible widget aspect ratio, allowing widgets to
maximize the real estate on compact screens. It also changes how the
grid content paddings are calculated. For compact screens, we now
calculate the top and bottom paddings needed for edit mode, and
distribute them evenly on each side for non edit mode. This ensures that
widget size remains consistent between the two modes, and only the
positions may shift vertically.

Test: visually; see recordings in bug
Bug: 419357983
Bug: 419361764
Flag: com.android.systemui.communal_responsive_grid
Flag: com.android.systemui.hub_edit_mode_transition
Change-Id: I51b803dbbf37a90e78f2bdbe748c44a8805789a8