Expose Telecom constants for use in Telephony

Expose Telecom constants that are used in Telephony in preparation for
mainline. Exposure is a combination of public/system -- those which made
sense for 3pty apps to access were made public.

Fixes: 168551099
Test: atest CtsTelecomTestCases
Change-Id: I688f04ba4ddf0498bad3463888fae71cdff2844a