Fix resize frame drawing underneath content

This sets a z-order on the content being resized, so that it is always
drawn above other content in the grid. This ensures the resize frame
shows up on top of other content.

Flag: com.android.systemui.communal_widget_resizing
Fixes: 372228411
Test: manually by expanding/shrinking widgets in the grid
Change-Id: I01390126c6fd0145efe212de292fba25ac45ad45