Embed CustomizationPickerFragment2 in CustomizationPickerActivity2 (2/2)

This is a preparation work for frag transition to CategoriesFragment

Test: Manully tested that the UI does not change
Bug: 368343524
Flag: com.android.systemui.shared.new_customization_picker_ui
Change-Id: I41c611962e8fac85f7fe9b04810d031165fc825b