IMS: Add support for STK CC feature

-- Add interface in IImsUtListener to get data for
   UNSOL_ON_SS.
-- Add new file ImsSsData to store the data received
   as part of UNSOL_ON_SS.
-- Add approprate error codes and strings to support
   to show error dialogs to user.
-- Add ImsUtInterface API's to indicate UNSOL_ON_SS
   to ImsPhoneCallTracker.

Test: Manual
Bug: 64685331
Change-Id: I023c1af0d521e5b19ecce1576c4caa299ae468e3