[36/N] Desks: Activate desk of launching task if inactive

Activates the desk of the launching / moving-to-front task instead of
activating the default desk is none are active. This ensures that
unminimizing a task from an inactive desk reactivates that desk.

This change also moved the order in which desks transitions are
processed, moving it to FreeformTasksTransitionObserver to guarantee
desk-level activation changes happen before DesktopTaskChangeListener
attempts to move freeform tasks into the current active desk.

Flag: com.android.window.flags.enable_multiple_desktops_backend
Bug: 391485148
Bug: 393978427
Bug: 390692038
Test: open a couple of freeform apps in desk#1, minimize one, then:
 1) Create and active desk#2 via adb commands
 2) Unminimize the task from the taskbar
 3) Verify desk#1 was reactivated with the unminimized task
 4) Dump DesktopRepository state and check tasks are under desk#1 and
    desk#1 is the active desk.

Change-Id: I3de82638c551857882ee48f9353cb3ec13b970f1