Exit desktop windowing transition

- Added `FreeformTaskTransitionStarterInitializer` to extract transition
  starter setup logic from `FreeformTaskTransitionHandler`.
- Added `DesktopMixedTransitionHandler` to coordinate desktop task close
  transition animation between Launcher (via `dispatchTransition`),
  `CloseDesktopTaskTransitionHandler` and fallback `FreeformTaskTransitionHandler`.
- Added `CloseDesktopTaskTransitionHandler` to animate close desktop
  window transition, when not leaving desktop mode.

Bug: 331165070
Test: atest WMShellUnitTests:DesktopMixedTransitionHandlerTest WMShellUnitTests:CloseDesktopTaskTransitionHandlerTest
Flag: com.android.window.flags.enable_desktop_windowing_exit_transitions
Change-Id: Ic5bf3673a5f5e8ae2fa22a9d3dbe77cefd244cb9
diff --git a/libs/WindowManager/Shell/Android.bp b/libs/WindowManager/Shell/Android.bp
index f857429..a796ecc 100644
--- a/libs/WindowManager/Shell/Android.bp
+++ b/libs/WindowManager/Shell/Android.bp
@@ -220,6 +220,7 @@
         "//frameworks/libs/systemui:com_android_systemui_shared_flags_lib",
         "//frameworks/libs/systemui:iconloader_base",
         "com_android_wm_shell_flags_lib",
+        "PlatformAnimationLib",
         "WindowManager-Shell-proto",
         "WindowManager-Shell-lite-proto",
         "WindowManager-Shell-shared",