fix(medusa): Incorrect swap difference due (#2086)

### What
Creating a swap on an order with a discount leads to an incorrect difference due. 

**Scenario**
- Create a store with minimum 2 products (Prod A, Prod B)
- Create a discount that only works for Prod A
- Create an order for Prod A with the discount applied
- Create a swap between Prod A and Prod B

**Expected outcome**
We would expect the difference_due amount to come out to the sum of:
- -1 * (price of prod a - discount applied to prod a) 
- price of prod b

**Actual outcome**
Instead the discount is applied across both products when calculating difference due. This results in a total that is instead the sum of:
- -1 * (price of prod a - discount applied to prod a)
- price of prod b - discount on prod b ignoring the condition

### How
Adds `line_item.adjustments` to relations in cart retrieval prior to setting the difference_due to car total

Fixes CORE-361

integration-tests/api/factories/simple-shipping-option-factory.ts

@@ -1,11 +1,11 @@
-import { Connection } from "typeorm"
-import faker from "faker"
 import {
+  ShippingOption,
   ShippingOptionPriceType,
   ShippingProfile,
-  ShippingOption,
   ShippingProfileType,
 } from "@medusajs/medusa"
+import faker from "faker"
+import { Connection } from "typeorm"
 
 export type ShippingOptionFactoryData = {
   name?: string