use sendable struct instead of class

[charliecruzan-stripe]

Summary

The problem here is that a call within the stripe-ios library to initialize a PKPaymentAuthorizationResult is passing the error that we pass in from RN, which conforms to this class, which is not "sendable". but PKPaymentAuthorizationResult expects that it is sendable. classes can be made sendable, but we should just use a struct here

Motivation

fixes #1748

Testing

• I tested this manually
• I added automated tests

Documentation

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• I have added relevant documentation for my changes.
• This PR does not result in any developer-facing changes.