Added serial number and timestamp in cell broadcat metrics

The timestamp logging helps analyzing the delivered time
of emergency alerts among devices.

Test: Telephony sanity tests
Bug: 113688249
Change-Id: Ie0b3dc7a876bbc8b14b1b85c099d94a5a9480f74
(cherry picked from commit 9f8a1f433e57495e4ecb45d10f86a01e3d35539b)
3 files changed