Migrate to StoreKit 2

[twodayslate]

SwiftyStoreKit isn't playing friendly with the new Xcode StoreKit testing.

Thought about moving to RevenueCat but with the recent launch of StoreKit 2 I'll just use that instead

• https://docs.revenuecat.com/docs/launch-checklist

• https://docs.revenuecat.com/docs/getting-started

• App Privacy requirements are minimal so I feel safe adding RevenueCat to NetUtils

• [ ] Xcode StoreKit Testing files

• [ ] Remove SwiftStoreKit

[twodayslate]

Perhaps StoreKit 2 would be better https://developer.apple.com/videos/play/wwdc2021/10114/

[twodayslate]

Partially implemented in #69