Update picture-in-picture settings to match mocks.

- Removing switches in top-level picture-in-picture settings, adding
  details screen for each app which contains the switch and some
  additional information.

Bug: 35957404
Test: make -j40 RunSettingsRoboTests
Change-Id: Ib22df8a52ab857e071ec43dd3e5d1f5282db35cb

res/xml/special_access.xml

@@ -79,6 +79,7 @@
         android:title="@string/picture_in_picture_title"
         android:fragment="com.android.settings.applications.PictureInPictureSettings"
         settings:keywords="@string/picture_in_picture_keywords" />
+
     <Preference
         android:key="premium_sms"
         android:title="@string/premium_sms_access"