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/applications/PackageManagerWrapperImpl.java

@@ -24,12 +24,18 @@ import android.content.pm.ResolveInfo;
 import java.util.List;
 
 public class PackageManagerWrapperImpl implements PackageManagerWrapper {
+
     private final PackageManager mPm;
 
     public PackageManagerWrapperImpl(PackageManager pm) {
         mPm = pm;
     }
 
+    @Override
+    public PackageManager getPackageManager() {
+        return mPm;
+    }
+
     @Override
     public List<ApplicationInfo> getInstalledApplicationsAsUser(int flags, int userId) {
         return mPm.getInstalledApplicationsAsUser(flags, userId);