[Settings] init UI entry for Cross SIM calling

Create an empty UI entry for Cross SIM calling.

TODO: fill-in implementation based on UI within document.

Document:
https://docs.google.com/document/d/1INEwrq5_M62hJcRMshdO0OaFruVR0goYByxdpMdFr_o/edit?disco=AAAAHQo7ang&ts=5fadc9b4&usp_dm=true#heading=h.8gw4a7e503pz

Bug: 174012397
Test: manual
Change-Id: I344a18954924c4665295ef244bfee773f3f98d55

src/com/android/settings/network/telephony/CrossSimCallingPreferenceController.java

@@ -0,0 +1,65 @@
+/*
+ * 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.network.telephony;
+
+import android.content.Context;
+
+/**
+ * Preference controller for "Cross SIM Calling"
+ **/
+public class CrossSimCallingPreferenceController extends TelephonyTogglePreferenceController {
+
+    /**
+     * Class constructor of cross sim calling.
+     *
+     * @param context of settings
+     * @param key assigned within UI entry of XML file
+     **/
+    public CrossSimCallingPreferenceController(Context context, String key) {
+        super(context, key);
+    }
+
+    /**
+     * Initialization based on given subscription id.
+     *
+     * @param subId is the subscription id
+     * @return this instance after initialization
+     **/
+    public CrossSimCallingPreferenceController init(int subId) {
+        return this;
+    }
+
+    @Override
+    public int getAvailabilityStatus(int subId) {
+        return CONDITIONALLY_UNAVAILABLE;
+    }
+
+    /**
+     * Implementation of abstract methods
+     **/
+    public boolean setChecked(boolean isChecked) {
+        return false;
+    }
+
+    /**
+     * Implementation of abstract methods
+     **/
+    public boolean isChecked() {
+        return false;
+    }
+
+}

src/com/android/settings/network/telephony/MobileNetworkSettings.java

@@ -173,8 +173,11 @@ public class MobileNetworkSettings extends AbstractMobileNetworkSettings {
 
         final VideoCallingPreferenceController videoCallingPreferenceController =
                 use(VideoCallingPreferenceController.class).init(mSubId);
+        final CrossSimCallingPreferenceController crossSimCallingPreferenceController =
+                use(CrossSimCallingPreferenceController.class).init(mSubId);
         use(CallingPreferenceCategoryController.class).setChildren(
-                Arrays.asList(wifiCallingPreferenceController, videoCallingPreferenceController));
+                Arrays.asList(wifiCallingPreferenceController, videoCallingPreferenceController,
+                        crossSimCallingPreferenceController));
         use(Enhanced4gLtePreferenceController.class).init(mSubId)
                 .addListener(videoCallingPreferenceController);
         use(Enhanced4gCallingPreferenceController.class).init(mSubId)