[1/n] Unify `DesktopModeStatus` between Shell and Sysui

Move `DesktopModeStatus` to shell/shared to remove code duplication
between Shell and Sysui.

Flag: None
Bug: 335401172
Test: atest WMShellUnitTests:DesktopModeLoggerTransitionObserverTest
Test: atest WMShellUnitTests:DesktopTasksControllerTest
Test: atest WMShellUnitTests:DesktopTasksLimiterTest
Test: atest WMShellUnitTests:FreeformTaskListenerTests
Test: atest WMShellUnitTests:RecentTasksControllerTest
Test: atest WMShellUnitTests:DesktopModeWindowDecorViewModelTests
Test: atest WMShellUnitTests:DesktopModeWindowDecorationTests
Test: atest WMShellUnitTests:WindowDecorationTests

Change-Id: I572dd6d9d777417c48636b2a49514aa99714561e