Update taskbar rounding when dragging or resizing desktop task.

If a maximized Desktop task is resized the Taskbar should be updated to
not be rounded. With this CL we trigger taskbar rounding once during
desktop task drag/resizing the first time a "move" is registered.

Bug: 431993211
Flag: EXEMPT bugfix
Test: MultiDisplayVeiledResizeTaskPositionerTest
Change-Id: Ia842deaf4a3ec42a495ab1e8b98a1f83912443ef