Added area info support in cell broadcast service

Added a broadcast for area info changed event, and
also a get method in cell broadcast service to
retrieve the area info.

Test: Cell broadcast sanity tests
Bug: 141318859
Merged-In: I682e579d797c35f1de032b93e0e0eb05e15928e0
Change-Id: I682e579d797c35f1de032b93e0e0eb05e15928e0
(cherry picked from commit 90af67b5480d9f2edf199bc0daf45d0019a6bf32)
6 files changed