Evaluate and create a wrapping class to return results from the payment APIs after `showPaymentSelector` is triggered

The intention of this plugin is to support as many payment providers as it's useful to developers. Each provider offers diverse forms of presenting information to return results and errors back to the caller, with JSON being a common format.

Let's evaluate how developers typically interact with this information and offer typed structures for those elements or pieces of information that are handled and processed programmatically (eg.: result/error class, display items, etc) and default to a more generic format for chunks of information (eg.: JSON) that are relied to other systems (eg.: backend, PSP).

Start by reviewing the payment APIs and the showPaymentSelector flow to understand how providers currently return results and errors. Done means defining an agreed typed structure for information handled programmatically while preserving a generic format such as JSON for provider-specific data.