Desks: Ensure freeform launches land inside a desk

When a launching a freeform task, if it's launching over an existing
active desk or causing a desk to become active, make sure it is always
reparented to the desk to prevent it from being a direct child of the
TDA.

This change includes a minor refactor to clarify whether a desk was
active prior to the launch and whether the launch will result in a desk
becoming active, staying active, or the task will exit desktop instead.

Flag: com.android.window.flags.enable_multiple_desktops_backend
Bug: 407602007
Test: while outside of desktop (home or fullscreen task visible) launch
a freeform task with adb command (as would CTS) and verify the desk
becomes active

Change-Id: Ide06daaf21e97a31066d5fc474ce0b3b2acff4f7