[33/N] Desks: Replace #bringDesktopAppsToFront usages

Replaces existing #bringDesktopAppsToFront callers with the multi-desk
compatible #addDeskActivationChanges.

This is mostly a refactor, except in:
1) #handleFreeformTaskLaunch, where prior to this change the return
   value (the minimized task) was not added as a pending minimized
   change even though the minimization WCT changes were applied.
   See Ibc697a4b0dff6a0b1583018d802b5caa66814220 where it was first
   added.
2) #handleFullscreenTaskLaunch, where prior to this change the
   task-limit logic could run twice: once in bringDesktopAppsToFront
   (without saving the pending minimized change) and another time
   through addAndGetMinimizedChanges (with saving of the pending
   minimized change).
   See Ia3419f2924e05f8f4cb607678f74c048bb888377 where it was first
   added.

Flag: com.android.window.flags.enable_multiple_desktops_backend
Bug: 362720497
Test: atest WMShellUnitTests
Change-Id: I49f46058c121d25f345860412336652939d5e3b1