Create arrow timezone interface and wrapper

Feature Request

It would be useful for users to directly import an arrow timezone object and create Arrow timezones rather than having to use datetime.timezone, ZoneInfo, or dateutil.tz.gettz. This will allow for full feature encapsulation within Arrow, so users can create timezones like this:

import arrow
arrow.now(tz=arrow.timezone("US/Pacific"))

This arrow.timezone wrapper can simply wrap the TzinfoParser and dateutil.tz.gettz logic and expose an easy-to-use interface for users.