Update widget editing highlight to match specs

This change moves the widget highlight underneath the widget and
offsets it to have some padding between the highlight and the
widget. We draw the highlight outside the bounds of the widget so that
we don't have to adjust all of the lazy grid dimensions.

Bug: 332596951
Bug: 349204822
Fix: 332596951
Fix: 349204822
Flag: com.android.systemui.communal_hub
Test: manually tested on device, also verified the highlight is not
      focusable with talkback on
Change-Id: Icfac603c3582f79b835015f408c2780c55256cee