Use same instance of TelephonyManager in PhoneAccountRegistrar.

Re-use the same instance of TelephonyManager in PhoneAccountRegistrar to
enable use of the property invalidated cache added there.

Test: Added unit test which confirms the number of AIDL calls when the
cache is operating as expected.
Test: Manual test; verified that I can see the property invalidated cache
logs which indicate that there are cache hits going on.
Bug: 224654574

Change-Id: I97a9713ffd840556328b8ae0aad9be8531434b7e