Fix fail to search by input "4G Calling"

Fixed step:
1.Update resource xml file in SearchIndexProvider.
2.Add keywords for preference title array.
3.Initizlize data member.
When getAvailabilityStatus called by updateNonIndexableKeys,
the data member should be initialized,
otherwise it always returns CONDITIONALLY_UNAVAILABLE

Fixes: 137155154
Test: manual
Change-Id: Id06d78bffdeba247741dcfe81e9ed7e179141397

res/values/strings.xml

@@ -7437,6 +7437,9 @@
     <!-- Battery Saver: Search terms for battery saver schedule preference. Feel free to add additional terms when translating if appropriate [CHAR_LIMIT=NONE] -->
     <string name="keywords_battery_saver_schedule">routine, schedule, battery saver, power saver, battery, automatic, percent</string>
 
+    <!-- List of synonyms for the enhance 4G LTE titles, used to match in settings search [CHAR LIMIT=NONE] -->
+    <string name="keywords_enhance_4g_lte">volte, advanced calling, 4g calling</string>
+
     <!-- Option title for the default sound, context based on screen -->
     <string name="default_sound">Default sound</string>