text: Title: Orders API: Use `get_unprefixed_state` for state output to strip country prefix
  Body: Stripe Tax uses `ISO 3166-2` with subdivisions to perform a lookup on tax rates, e.g `country-state`, which makes sense. On checkout we therefore store the state in this format too for tax calculations.
  
  However, customers expect a separation. Getting country from `orders.billing_address.country` and state from `orders.billing_address.state` (clean from country codes).
  
  So our output of the schema should use `get_unprefixed_state` to strip the country code from the state output in our API.