US Region referenced by alias rather than object

[Rockerby]

I've been working through a site which uses this provider in conjunction with the Vendr Checkout plugin and came across an issue when sending payment info for the US. Opayo requires the region to be provided and in this provider we're finding this by alias reference - where the region is stored against the PaymentInfo object.

I think that it should fetch the region in the same way that it fetches the country, through the PaymentInfo object (rather than attempting to fetch it via an alias). Does this sound like a sensible way forward? I'm happy to create a PR for the work.

Specifically in this code and for reference, here is where it's being stored in the Checkout plugin.