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

packages/medusa/src/interfaces/index.ts

@@ -10,3 +10,4 @@ export * from "./models/base-entity"
 export * from "./models/soft-deletable-entity"
 export * from "./search-service"
 export * from "./payment-service"
+export * from "./services"

packages/medusa/src/interfaces/services/cache.ts

@@ -0,0 +1,7 @@
+export interface ICacheService {
+  get<T>(key: string): Promise<T | null>
+
+  set(key: string, data: unknown, ttl?: number): Promise<void>
+
+  invalidate(key: string): Promise<void>
+}

packages/medusa/src/interfaces/services/index.ts

@@ -0,0 +1 @@
+export * from "./cache"