[Divider] Add Operation to boost the decor surface

This is needed to draw the veils on the decor surface when dragging the
divider. A cover surface is added to ensure that the content of the
below windows are invisible.

Bug: 293654166
Test: atest TaskTests
Change-Id: I894528a6eb7880deb94cb04893ec8eea42c062b5
5 files changed