Add search loader for installed apps.

- The loader filters out system apps.
- Loader performs case-insensitive match with app names.
- SearchResultAdapter combines results from multiple loaders into a
  single list.

Fixes: 33347966
Test: make RunSettingsRoboTests
Change-Id: I228ca6fb82f0ac5151b2346c079c2de41104a4df

src/com/android/settings/search2/DatabaseResultLoader.java

@@ -23,10 +23,11 @@ import android.database.Cursor;
 import android.database.sqlite.SQLiteDatabase;
 import android.graphics.drawable.Drawable;
 import android.support.annotation.VisibleForTesting;
+
+import com.android.settings.R;
 import com.android.settings.search.Index;
 import com.android.settings.search.IndexDatabaseHelper;
 import com.android.settings.utils.AsyncLoader;
-import com.android.settings.R;
 
 import java.util.ArrayList;
 import java.util.Collections;
@@ -107,7 +108,6 @@ public class DatabaseResultLoader extends AsyncLoader<List<SearchResult>> {
                 icon = mContext.getDrawable(R.drawable.ic_search_history);
             }
 
-
             SearchResult.Builder builder = new SearchResult.Builder();
             builder.addTitle(title)
                     .addSummary(summaryOn)