"Rewrite" PhoneNumberUtil so that it compares two phone strings using as many...

"Rewrite" PhoneNumberUtil so that it compares two phone strings using as many characters as possible, unlike the previous implementation.
The new implementation considers country code seriously.

To confirm this change does not do something wrong, I also created another change (https://android-git.corp.google.com/g/Gerrit#change,4036).
All tests related to PhoneNumberUtils pass, including Thailand's ugly buggy behavior around country code handling :-P

Also Add tests for PhoneNumberUtils, which can be executed in the usual workstation like this:
> g++ -Wall external/sqlite/android/PhoneNumberUtils.cpp external/sqlite/android/PhoneNumberUtilsTest.cpp
> ./a.out

This change fixes the internal bug 1868702.