Unify the default template and title

On AppDataUsage page, using single source of truth to calculate the
default template, and set title base on the current template.

Fix: 213266028
Fix: 234104784
Test: visual - on AppDataUsage
Test: unit test
Change-Id: I80facca0b000964e901905af51a344a4bc9f498b

src/com/android/settings/datausage/BillingCycleSettings.java

@@ -44,6 +44,7 @@ import androidx.preference.SwitchPreference;
 
 import com.android.settings.R;
 import com.android.settings.core.instrumentation.InstrumentedDialogFragment;
+import com.android.settings.datausage.lib.NetworkTemplates;
 import com.android.settings.network.SubscriptionUtil;
 import com.android.settings.network.telephony.MobileNetworkUtils;
 import com.android.settings.search.BaseSearchIndexProvider;
@@ -128,8 +129,7 @@ public class BillingCycleSettings extends DataUsageBaseFragment implements
         }
 
         if (mNetworkTemplate == null) {
-            mNetworkTemplate = DataUsageUtils.getDefaultTemplate(context,
-                DataUsageUtils.getDefaultSubscriptionId(context));
+            mNetworkTemplate = NetworkTemplates.INSTANCE.getDefaultTemplate(context);
         }
 
         mBillingCycle = findPreference(KEY_BILLING_CYCLE);