Setup backup calling for new UI

Backup calling new handles by CrossSimCallingViewModel.
CrossSimCallingViewModel keep monitoring the active SIMs, and setup
backup calling if needed.

Fix: 340444839
Test: manual - SIMs
Test: manual - Mobile Settings
Test: unit test
Change-Id: I0a3451f1e8c3984b2348cf628fb1d91ce7aaecec

src/com/android/settings/network/ProxySubscriptionManager.java

@@ -28,7 +28,6 @@ import android.telephony.SubscriptionManager;
 import android.util.Log;
 
 import androidx.annotation.Keep;
-import androidx.annotation.NonNull;
 import androidx.annotation.VisibleForTesting;
 import androidx.lifecycle.Lifecycle;
 import androidx.lifecycle.LifecycleObserver;
@@ -242,15 +241,6 @@ public class ProxySubscriptionManager implements LifecycleObserver {
         return mSubscriptionMonitor.getAccessibleSubscriptionInfo(subId);
     }
 
-    /**
-     * Gets a list of active, visible subscription Id(s) of the currently active SIM(s).
-     *
-     * @return the list of subId's that are active and visible; the length may be 0.
-     */
-    public @NonNull int[] getActiveSubscriptionIdList() {
-        return mSubscriptionMonitor.getActiveSubscriptionIdList();
-    }
-
     /**
      * Clear data cached within proxy
      */