Implement urRouteParamenters method in commerce_order_item entity

Describe your bug or feature request.

Follow-up from 🐛 Not compatible with devel module Active , where there is an incompatibility between devel and commerce order item UI modules because devel module is not capable to build the URL properly because the order parameter is missing.

Our suggested approach is to implement the urlRouteParameters method in OrderItem class, in a similar way as other commerce order related entity types do. See Payment, ProductVariation, PaymentMethod or Coupon.

If a bug, provide steps to reproduce it from a clean install.

• Install Commerce Order Item UI module in a vanilla commerce site
• Install devel
• Create an order
• Visit the order page (admin/commerce/orders/X)
• Click on the Order Items tab
• Fatal error is thrown

Update IS.

Change looks ok to me and is not really invasive, so merged it! thanks!

Thanks! Could this change be backported to 2.x branch?