Add KEY_CARRIER_USSD_METHOD_INT to specify methods for USSD requests

Bug: 171417408
Test: atest ImsPhoneTest, atest CarrierConfigManagerTest

Change-Id: If73b775baac47b3bc85507e778e436b5a67f8017
Merged-In: I6a6bfd5e2945ea6aed897896bdbeee244dc0dcc3
3 files changed