Call waiting support USSD function

-Add USSD function
-Call waiting uses TelephonyManager's get/set methods
Bug: 180540626
Test: build pass. Manual test: set/get call waiting.

Change-Id: Ia03fd4ddef1defb1f0f9091c58ab0f1e43936457
Merged-In: Ia03fd4ddef1defb1f0f9091c58ab0f1e43936457
6 files changed