Add "New Window" option to Taskbar menu.

This change adds a new menu option to Taskbar that is invoked when long
pressing an icon. It createds a new instance for an app if the app
supports multi instance in Desktop Mode.

Bug: 315344726
Test: Manual
Flag: com.android.launcher3.enable_multi_instance_menu_taskbar
Change-Id: Ibc42fbb1ad485496cd938af730b86e051cea559a