[Wi-Fi][A11Y] Fix TalkBack lose focus in WifiSettings & WifiSettings2

Use stable ID feature of RecycleView to keep preference focus.

Bug: 126132618
Test: WifiSettingsTest
      WifiSettings2Test
      manual visual

Change-Id: Id73157b0935186c9a59d1ef68190d853f671ebc2

tests/robotests/src/com/android/settings/wifi/WifiSettingsTest.java

@@ -45,6 +45,8 @@ import android.view.View;
 
 import androidx.fragment.app.FragmentActivity;
 import androidx.preference.Preference;
+import androidx.preference.PreferenceScreen;
+import androidx.recyclerview.widget.RecyclerView;
 
 import com.android.settings.R;
 import com.android.settings.datausage.DataUsagePreference;
@@ -291,4 +293,13 @@ public class WifiSettingsTest {
 
         verify(menu).add(anyInt(), eq(WifiSettings.MENU_ID_FORGET), anyInt(), anyInt());
     }
+
+    @Test
+    public void onCreateAdapter_hasStableIdsTrue() {
+        final PreferenceScreen preferenceScreen = mock(PreferenceScreen.class);
+
+        RecyclerView.Adapter adapter = mWifiSettings.onCreateAdapter(preferenceScreen);
+
+        assertThat(adapter.hasStableIds()).isTrue();
+    }
 }