This was a regression introduced by #3605.
### Example:
Consider a paywall configuration with these locales: `en_US`, `de_DE`.
Running on a device with locale `en_IN` for example.
Before #3605, `PaywallData.localizedConfiguration` would have returned
the `en_US` localization. However, that change made it so that it could
no longer find a matching localization with a different region.
This fix improves the locale lookup so that if it doesn't find a
matching localization with both language AND region, it then tries to
look it up with only the language, before falling back to the default
localization.
Apple changed `xrOS` to `visionOS` on the latest beta. Looks like this
was already supported in prior `Xcode 15.1` betas, so this doesn't break
compatibility with them.
NachoSoto