Settings search - Navigate user to exact page

- remove duplicate index preference
- default set searchable = false when the preference has fragment
- make some fragments indexable

Bug: 143057584
Test: robotest & manual

Change-Id: I4d64f6106d2f92f0a45e8c7e26388677f593f412

res/xml/automatic_storage_management_settings.xml

@@ -16,6 +16,7 @@
 
 <PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android"
         xmlns:settings="http://schemas.android.com/apk/res-auto"
+        android:key="automatic_storage_manager_screen"
         android:title="@string/automatic_storage_manager_settings" >
 
         <DropDownPreference