cellbroadcast provider refactor

1. expose proper APIs to query framework cellbroadcast provider
2. export framework cellbroadcast provider
3. new URI with proper permission check

Bug: 135956699
Test: Build & Manual
Change-Id: I2f0ab939eb0e041900c112386117e90404b37452
(cherry picked from commit 34c7167644be17ab67e96aead95a7c0d07c0dcec)
Merged-in: I2f0ab939eb0e041900c112386117e90404b37452
2 files changed