Add PhoneAccountHandle method to check if 2 accts are from same CS.

Add a new PhoneAccountHandle method to check if 2 phone account handles
are from the same connectionservice (package).

Test: Manual testing.
Test: Added new unit tests for this new method.
Bug: 129505115
Change-Id: I85eca54340e79d4a4f189188ae787201bab1724e
1 file changed