Better timezone detection for phones via phonenumbers

[tsx]

This switches phone tz detection from indirect (phone -> address -> tz) to direct phonenumbers call.

It is now simpler, faster, significantly more precise outside of US, and saves a whopping 100MB of RAM per process by not using (and not loading) phonenumbers' geocoder.

[tsx]

Just to clarify: judging by initial test failures, our prefix-based AU state detection appears to be more precise than phonenumbers' so I left it there. For US/CA phonenumbers' seems to be fine though.