Move physical keyboard search landing page to its Fragment

This CL moves the code building index of physical keyboards from
InputMethodAndLanguageSettings to PhysicalKeyboardFragment, so that a
search landing page becomes PhysicalKeyboardFragment as expected.

Bug: 32643633
Test: Connecting/Disconnecting Anker bluetooth keyboard while Settings
      app is/isn't running, the search Anker and verify landing page
      is PhysicalKeyboardFragment.
Test: Update robolectric DynamicIndexableContentMonitorTest.

Change-Id: I51f308ada74966a96c258f8ef50a9b4fc7bc6635

src/com/android/settings/search/DynamicIndexableContentMonitor.java

@@ -48,6 +48,7 @@ import android.view.inputmethod.InputMethodManager;
 import com.android.internal.content.PackageMonitor;
 import com.android.settings.accessibility.AccessibilitySettings;
 import com.android.settings.inputmethod.InputMethodAndLanguageSettings;
+import com.android.settings.inputmethod.PhysicalKeyboardFragment;
 import com.android.settings.print.PrintSettingsFragment;
 
 import java.util.ArrayList;
@@ -205,8 +206,7 @@ public final class DynamicIndexableContentMonitor implements
         }
 
         private void buildIndex(boolean rebuild) {
-            // TODO: Fix landing page to PhysicalKeyboardFragment.
-            mIndex.updateFromClassNameResource(InputMethodAndLanguageSettings.class.getName(),
+            mIndex.updateFromClassNameResource(PhysicalKeyboardFragment.class.getName(),
                     rebuild, true /* includeInSearchResult */);
         }