Remove hidden Telephony API usages from Telecom

Inline utility methods from BlockChecker and
AsyncEmergencyContactNotifier, and use the new API from
TelephonyRegistryManager in PhoneStateBroadcaster.

Also fix a flaky test

Bug: 141576016
Fixes: 144264937
Test: unit, cts
Change-Id: I6108d0e1c97f15b096c8b07f529edf5c3a7ee058