Telephony: STK CC feature implementation

Add strings and constants required for stk cc feature.

Change-Id: Id5ec987cdc8dc2d9eebdf01fe546eb96ec0c69f9
(cherry picked from commit 0647546916683963ba5191b4d013bd6ff3c7483d)
(cherry picked from commit 17e39ecff8e0ab7590308e78a0b2cfcf728693d5)