Introduce boolean flags to show/hide items for Language & input.

This adds seven new boolean flags:
config_show_phone_language
config_show_virtual_keyboard_pref
config_show_physical_keyboard_pref
config_show_spellcheckers_settings
config_show_tts_settings_summary
config_show_pointer_speed
config_show_vibrate_input_devices

Which when individually set to false, will hide the item from "Language
& input" in System. It will also hide them from surfacing in search
results.

Bug: 62379555
Test: Individual controller tests are all updated.

Change-Id: I9ef1c3037b0bec6ffa5a627006507f4f16e534c4

src/com/android/settings/inputmethod/SpellCheckerPreferenceController.java

@@ -51,7 +51,7 @@ public class SpellCheckerPreferenceController extends AbstractPreferenceControll
 
     @Override
     public boolean isAvailable() {
-        return true;
+        return mContext.getResources().getBoolean(R.bool.config_show_spellcheckers_settings);
     }
 
     @Override