Use TelecomManager to call TelephonyManager#getVoicemailNumber (1/2)

Since we don't want the phone app to call TelephonyManager methods
directly, create a method in TelecomManager to mimic the behavior. The
reason we don't return the voicemail number directly is because once
TelecomManager becomes public, we don't want any old app to be able to
get the SIM's voicemail number.

Bug: 18233678

Change-Id: I620af409788aea7b58169b72a563baeed8115080
diff --git a/telecomm/java/com/android/internal/telecom/ITelecomService.aidl b/telecomm/java/com/android/internal/telecom/ITelecomService.aidl
index cbd9d69..f8d7539 100644
--- a/telecomm/java/com/android/internal/telecom/ITelecomService.aidl
+++ b/telecomm/java/com/android/internal/telecom/ITelecomService.aidl
@@ -121,6 +121,11 @@
     boolean isVoiceMailNumber(in PhoneAccountHandle accountHandle, String number);
 
     /**
+     * @see TelecomServiceImpl#hasVoiceMailNumber
+     */
+    boolean hasVoiceMailNumber(in PhoneAccountHandle accountHandle);
+
+    /**
      * @see TelecomServiceImpl#getDefaultPhoneApp
      */
     ComponentName getDefaultPhoneApp();