Fix plugin definition to be compatible with commerce-3.x

Problem/Motivation

The payment gateway plugin is not defined correctly. Specifically, important attributes such as the payment type and default forms (e.g., refund-payment) are missing. These attributes are normally provided through the PaymentGatewayBase::create() method.

In Commerce 3.x, payment gateway plugins must be created using the create() factory method rather than the constructor. To ensure compatibility, our custom gateway plugins must also adopt this approach.

Steps to reproduce

1. Install Commerce.
2. Install commerce_2c2p.
3. Create a new payment using the 2C2P gateway.
4. Attempt to refund the payment.

Result: An error is thrown stating that the refund-payment form is missing from the plugin definition.

Proposed resolution

Update the plugin to use the new instance creation pattern introduced in Commerce 3.x:

• Move all service injections and property assignments into the create() method.
• Stop relying on the constructor for dependency injection.
• Ensure default forms (such as refund-payment) are properly set.