Add quick switch flag for desktop windowing cases.

Add quick switch flag to desktop windowing cases. Quick switch should
work out of the box for desktop windowing when the flag is enabled.

Bug: 322759294
Bug: 322759294
Test: Manually enable/disable the flag
Flag: ACONFIG com.android.window.flags.enable_desktop_windowing_quick_switch DEVELOPMENT

Change-Id: Ifb531368552449f70ce9d883418d26c7f272c6e9