Private space header to support RTL

bug:335658774
Test manually:
before: https://drive.google.com/file/d/1N8kFl28OhCJ7kTTo8VK74x-Mvaqi8GJ4/view?usp=sharing
after:https://drive.google.com/file/d/1N6AyVXcOSA48NveklIeqypueu7WLfP0V/view?usp=sharing
Flag: ACONFIG com.android.launcher3.enable_private_space TRUNKFOOD

Change-Id: I1c80e33f84251d42cd5821735457548de41db40d

res/layout/private_space_header.xml

@@ -24,6 +24,7 @@
         android:background="@drawable/bg_ps_header"
         android:clipToOutline="true"
         android:gravity="center_vertical"
+        android:textDirection="locale"
         android:orientation="horizontal">
 
     <LinearLayout