Add SearchIndexable to improve search coverage

- Add searachIndex test
- Increase accessibility framework feature fragment coverage

Bug: 197695932
Test: make RunSettingsRoboTests
Change-Id: Icb7e2cf70bb0443304af7866efd48bed1d9af5bf

tests/robotests/src/com/android/settings/accessibility/HearingAidPairingDialogFragmentTest.java

@@ -22,6 +22,7 @@ import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.when;
 import static org.robolectric.Shadows.shadowOf;
 
+import android.app.settings.SettingsEnums;
 import android.content.DialogInterface;
 import android.content.Intent;
 import android.os.Bundle;
@@ -102,4 +103,10 @@ public class HearingAidPairingDialogFragmentTest {
 
         assertThat(dialog.isShowing()).isFalse();
     }
+
+    @Test
+    public void getMetricsCategory_returnsCorrectCategory() {
+        assertThat(mFragment.getMetricsCategory()).isEqualTo(
+                SettingsEnums.DIALOG_ACCESSIBILITY_HEARING_AID_PAIR_ANOTHER);
+    }
 }