Use FooterPreference in AccountSyncSettings page

.Use the new FooterPreference and removed the old FooterPreferenceMixin
 from the AccountSyncSettings page.
.Add the ShadowAuthenticationHelper for commnon shadow util.

Fixes: 138978130
Test: manual test
Test: make RunSettingsRoboTests ROBOTEST_FILTER=com.android.settings.accounts
Change-Id: I93ae46b3b66e7e504320a9ed120ab7948dd06423

tests/robotests/src/com/android/settings/accounts/AccountSyncSettingsTest.java

@@ -15,6 +15,8 @@
  */
 package com.android.settings.accounts;
 
+import static com.google.common.truth.Truth.assertThat;
+
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.when;
@@ -24,7 +26,9 @@ import android.content.Context;
 import android.os.UserHandle;
 
 import androidx.fragment.app.FragmentActivity;
+import androidx.preference.Preference;
 
+import com.android.settings.testutils.shadow.ShadowAuthenticationHelper;
 import com.android.settings.testutils.shadow.ShadowContentResolver;
 
 import org.junit.After;
@@ -33,6 +37,7 @@ import org.junit.runner.RunWith;
 import org.robolectric.RobolectricTestRunner;
 import org.robolectric.RuntimeEnvironment;
 import org.robolectric.annotation.Config;
+import org.robolectric.shadows.androidx.fragment.FragmentController;
 import org.robolectric.util.ReflectionHelpers;
 
 @RunWith(RobolectricTestRunner.class)
@@ -57,4 +62,18 @@ public class AccountSyncSettingsTest {
         settings.onPreferenceTreeClick(preference);
         // no crash
     }
+
+    @Test
+    @Config(shadows = {ShadowAuthenticationHelper.class})
+    public void createFooterPreference_shouldReturnFooter() {
+        final AccountSyncSettings settings = FragmentController.of(new AccountSyncSettings())
+                .create()
+                .get();
+
+        settings.createFooterPreference();
+
+        final Preference footer = settings.getPreferenceScreen().findPreference(
+                "footer_preference");
+        assertThat(footer).isNotNull();
+    }
 }