fix(core-flows): copy line items attribute (#8471)

removing `requires_shipping` from variant won't be part of this PR

integration-tests/modules/__tests__/cart/store/carts.spec.ts

@@ -2032,6 +2032,7 @@ medusaIntegrationTestRunner({
               original_shipping_total: 0,
               items: [
                 expect.objectContaining({
+                  id: expect.stringContaining("ordli_"),
                   product_id: product.id,
                   unit_price: 100,
                   quantity: 1,