Reland add FeatureProvider for SyncAcrossDevices Settings integration.

Prior CL ag/26930404 was reverted because an unused class was
trimmed in AOSP, causing test cases to throw NoClassDefFoundError
exceptions. This CL combines ag/26930404 and ag/26995936 to address
the failure.

Bug: 330498032
Test: atest FakeFeatureFactory, atest SyncAcrossDevicesPreferenceControllerTest
Change-Id: I0a7ebccdebcad20e06d7542d7c4a0005885f393b

src/com/android/settings/notification/syncacrossdevices/SyncAcrossDevicesFeatureCallback.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.settings.notification.syncacrossdevices;
+
+import androidx.annotation.Nullable;
+import androidx.preference.Preference;
+
+/** Callback to add or remove {@link Preference} in Sync Across Devices feature. */
+public interface SyncAcrossDevicesFeatureCallback {
+
+    /**
+     * Called when a sync across devices feature is added
+     *
+     * @param preference present the feature
+     */
+    void onFeatureAdded(@Nullable Preference preference);
+
+    /**
+     * Called when a sync across devices feature is removed
+     *
+     * @param preference present the feature
+     */
+    void onFeatureRemoved(@Nullable Preference preference);
+}