UR-4807 Fix - Payments table product column empty when invoice_plan is not set

[MILAN88888]

All Submissions:

• Have you followed the User Registration Contributing guideline?
• Does your code follow the WordPress' coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

Jira: UR-4807

The payments table Product column read invoice_plan from ur_payment_invoices, which only Stripe subscriptions ever set. It was blank for Authorize.net, PayPal, Mollie and one-time payments.

Falls back to the labels stored in the cart items when invoice_plan is absent, so existing records are fixed too with no data migration. invoice_plan still wins when present, so Stripe is unchanged.

Keeps OrdersListTable.php in sync with wpeverest/user-registration-pro#1395.

How to test the changes in this Pull Request:

1. Go to Payments (Payment History).
2. Product column shows a value for Authorize.net, PayPal and Mollie records instead of being empty.
3. Stripe subscription records are unchanged.

Types of changes:

• Bug fix (non-breaking change which fixes an issue)

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you successfully ran tests with your changes locally?
• Have you updated the documentation accordingly?

Changelog entry

Fix - Payments table Product column was empty for Authorize.net, PayPal and Mollie payments.