Fix the Process Payment response specification to reflect the correct nested object structure.

[edgarmartinezlogos]

What changed?

This change adds the data property to the Process Payment response and nest the existing id, transaction_type, and status fields within it, consistent with other response objects in the V3 API (Example: Create Access Token https://github.com/bigcommerce/docs/blob/main/reference/payments/access-tokens_payments.v3.yml#L105)

Before

{
	"id": "",
	"transaction_type": "",
	"status": ""
}

Now

{
	"data": {
		"id": "",
		"transaction_type": "",
		"status": ""
	}
}

Why?

The BigCommerce Payments API is already returning a response that conforms to the updated specifications defined in this PR.