Accessibility shortcut primary action - setup entry for launched type fragment.

* Reduce the complexity of updateServicePreferences.
* Introduces RestrictedPreferenceHelper to setup installed
AccessibilityServiceInfo and AccessibilityShortcutInfo.

Bug: 142531433
Test: make RunSettingsRoboTests
Change-Id: I0f5eeac56a93caadeb05c25f1f8c4daa0d775b35

src/com/android/settings/accessibility/LaunchAccessibilityActivityPreferenceFragment.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright (C) 2020 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.accessibility;
+
+/** Fragment for providing open activity button. */
+public class LaunchAccessibilityActivityPreferenceFragment extends
+        ToggleFeaturePreferenceFragment {
+
+    @Override
+    protected void onPreferenceToggled(String preferenceKey, boolean enabled) {
+        // TODO(b/142531433): Added in next CL.
+    }
+}