Add test function for emergency number db update

1) get emergency number db version
2) override emergency db file partition

Test: atest TelephonyHostTest#testEmergencyNumberDb
(Though the condition is RVC, I manually triggered all the running with QT build,
 and ensured each Assert is hit)
https://paste.googleplex.com/4679407325151232
Bug: 136027884

Change-Id: I3a2f5a668d84804c80f94e2227c8e0d6c51e5153