Disable Desktop Windowing for devices with smaller screen sizes

For devices with screen size smaller than
`Configuration.SCREENLAYOUT_SIZE_XLARGE`, hide the desktop windowing app
handle and ignore `DesktopTaskController.moveToDesktop` calls. This
hides all the on screen entry points and disables the adb commands and
shortcuts to enter Desktop Windowing.

Fixes: 326957646
Test: atest WMShellUnitTests:DesktopModeWindowDecorViewModelTests
Test: atest WMShellUnitTests:DesktopTasksControllerTest
Change-Id: I6f3224052c7fd88beefb9e58b0009569376d3a62