Add support for rejecting Telecom call with a specified reason.

Piping through the reject with reason API.

Bug: 135929421
Test: Added new CTS test to validate API pathways.
Test: Ran existing telecom and telephony unit tests.
Test: Modified test dialer app to use the new reject API and verified that
the reject reason signals down to the modem and translates to the correct
reject cause.

Change-Id: I6782a502c62f1d0c6b6a8802bf17ea9b62621b34