Update API docs for Telephony call state reporting.

Update TelephonyManager#getCallState,
PhoneStateListener#onCallStateChanged to make it clear which calls each
method considers in determining call state.
Added intdef for call state (allows auto doc generation of valid
values for parameters).

Test: make docs
Bug: 73245376
Change-Id: I70ebd0f00ae3f0e1370ae275be8f8ef6f008523d