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
1 file changed