[Settings] Code Refactor

Code refactor in order to support auto testing

Bug:  140542283
Test: m RunSettingsRoboTests -j
ROBOTEST_FILTER=WifiCallingSettingsForSubTest

Change-Id: I2427732435b59d7359a102e0dd56317ac6a024b4

tests/robotests/src/com/android/settings/wifi/calling/WifiCallingSettingsForSubTest.java

@@ -351,5 +351,13 @@ public class WifiCallingSettingsForSubTest {
                     return null;
             }
         }
+
+        @Override
+        TelephonyManager getTelephonyManagerForSub(int subId) {
+            return mTelephonyManager;
+        }
+
+        @Override
+        void showAlert(Intent intent) {}
     }
 }