Ensure default and remote transition handlers are first

- When Transitions migrated to ShellInit, the default/remote handlers
  got added after PipTransitionController (which should really also
  use ShellInit (to be fixed in a follow up CL)).  For now, we can
  be explicit about where they should be added in the list.

Bug: 241515409
Bug: 241484248
Test: atest PinnedStackTests
Test: atest WMShellFlickerTests:com.android.wm.shell.flicker.pip.AutoEnterPipOnGoToHomeTest
Change-Id: I696327004e06e7ddd402a509fa18c86c60b244d4

libs/WindowManager/Shell/src/com/android/wm/shell/transition/Transitions.java

@@ -158,9 +158,9 @@ public class Transitions implements RemoteCallable<Transitions> {
 
     private void onInit() {
         // The very last handler (0 in the list) should be the default one.
-        mHandlers.add(mDefaultTransitionHandler);
+        mHandlers.add(0, mDefaultTransitionHandler);
         // Next lowest priority is remote transitions.
-        mHandlers.add(mRemoteTransitionHandler);
+        mHandlers.add(1, mRemoteTransitionHandler);
 
         ContentResolver resolver = mContext.getContentResolver();
         mTransitionAnimationScaleSetting = Settings.Global.getFloat(resolver,