Add cleaned up unit tests moved from platform

Bug: 135956699
Test: atest CellBroadcastServiceTests

Merged-In: I9b88b2f84ddb4250a435aa9292224620c990bbaa
Change-Id: I9b88b2f84ddb4250a435aa9292224620c990bbaa
(cherry picked from commit c8e1239c6c164c518c758c3b223533ddd6a98613)
4 files changed