Add configuration items for the terminal-based call waiting service

The following keys are added:
- KEY_TERMINAL_BASED_CALL_WAITING_SYNC_TYPE_INT
- KEY_TERMINAL_BASED_CALL_WAITING_DEFAULT_ENABLED_BOOL

Bug: 202463005
Test: atest FrameworksTelephonyTests:CallWaitingControllerTest
Change-Id: Id0a632dcef6caace6d798428388baf2727eb8d60
(cherry picked from commit a32fd53f1388f25ec4790132105f607db3258f44)
Merged-In: Id0a632dcef6caace6d798428388baf2727eb8d60