feat(medusa): Performance improvements of Carts domain (#2648)

**What**

I have created a new method on the cart service which is `addLineItems`, allowing a user to add one or multiple items in an optimized way. Also updated the `generate` method from the line item service which now also accept a object data or a collection of data which. Various places have been optimized and cache support has been added to the price selection strategy.

The overall optimization allows to reach another 9000% improvement in the response time as a median (Creating a cart with 6 items):

|   | Min (ms)  | Median (ms)  | Max (ms)  | Median Improvement (%)
|---|:-:|---|---|---|
| Before optimisation  | 1200  | 9999 | 12698  |  N/A
| After optimisation | 63  | 252  | 500  | 39x
| After re optimisation | 56 | 82  | 399  | 121x
| After including addressed feedback | 65 | 202  | 495  | 49x

FIXES CORE-722

integration-tests/api/factories/simple-price-list-factory.ts

@@ -1,8 +1,9 @@
 import {
-  PriceList,
+  CustomerGroup,
   MoneyAmount,
-  PriceListType,
+  PriceList,
   PriceListStatus,
+  PriceListType,
 } from "@medusajs/medusa"
 import faker from "faker"
 import { Connection } from "typeorm"
@@ -41,7 +42,7 @@ export const simplePriceListFactory = async (
 
   const listId = data.id || `simple-price-list-${Math.random() * 1000}`
 
-  let customerGroups = []
+  let customerGroups: CustomerGroup[] = []
   if (typeof data.customer_groups !== "undefined") {
     customerGroups = await Promise.all(
       data.customer_groups.map((group) =>