Integrate OTA emergency number database with EmergencyNumberTracker

Integrate OTA emergency number database with EmergencyNumberTracker,
 compare the OTA emergency number database and Asset emergency number
database, and pick up the higher-version database as the usage.

Fix a minor comment mistake.

Test: Manually configured a database in the corresponding file partition;
Observed the database is cached: https://paste.googleplex.com/6568325855313920

Bug: 136027884

Change-Id: I916cd7676ecaf0891e4c233fc78b623349135c2e