Add keyboard shortcuts implementation for Desktop Windowing task

resizing keyboard shortcuts (snap left/right, toggle window size and
minimize task)

Flag: com.android.window.flags.enable_task_resizing_keyboard_shortcuts
Test: atest DesktopModeKeyGestureHandlerTest
Bug: 335819608
Change-Id: I4c5318ccfda0043e13b377196cb35c78a7815da8