Adding callback support for Entering DesktopMode from DesktopTaskView

This cl inlcudes
	- callback for entry when user enters from existing DesktopTaskView in overview/recents

Test: Presubmit
Bug: 343882478
Flag: com.android.window.flags.enable_desktop_windowing_mode
Change-Id: I5553e49cbaa84ea663ec904d0efd2c2c07ae0547