Eliminate duplicate keys in pref xmls.

- Remove additional_system_update pref device_info page, we don't need
  it.
- Update keys in xml and Preference controller, and search index
  provider.
- Clean up in ScreenZoomPreference, it's anti-pattern to set fragment in
  constructor.
- Whitelist 2 that are super hard to remove.

Change-Id: Ibab6e2cb074513042a2ae007d9085aa64046eec8
Fixes: 67852637
Test: uniquePreferenceTest

src/com/android/settings/display/ScreenZoomPreference.java

@@ -34,10 +34,6 @@ public class ScreenZoomPreference extends Preference {
                 android.support.v7.preference.R.attr.preferenceStyle,
                 android.R.attr.preferenceStyle));
 
-        if (TextUtils.isEmpty(getFragment())) {
-            setFragment("com.android.settings.display.ScreenZoomSettings");
-        }
-
         final DisplayDensityUtils density = new DisplayDensityUtils(context);
         final int defaultIndex = density.getCurrentIndex();
         if (defaultIndex < 0) {