Using Desktop Windowing limit from config in E2E tests instead of hardcoding 4 apps limit

Bug: 372602695
Flag: EXEMPT no flag is needed for instrumented tests refactoring
Test: atest PlatformScenarioTests:com.android.wm.shell.functional.resizing.ResizeAppCornerMultiWindowTest && atest PlatformScenarioTests:com.android.wm.shell.functional.EnterDesktopWithDragExistingWindowsTest && atest PlatformScenarioTests:com.android.wm.shell.scenarios.EnterDesktopWithAppHandleMenuExistingWindows

Change-Id: I621780371326495215df34ca38576f68a768dd7d