feat(medusa): List (service + controller) product categories #3004 (#3023)

**What:**

Introduces a store endpoint to retrieve a list of product categories

**Why:**

This is part of a greater goal of allowing products to be added to multiple categories.

**How:**

- Creates an endpoint in store routes

RESOLVES CORE-968

packages/medusa/src/api/routes/admin/product-categories/list-product-categories.ts

@@ -18,6 +18,8 @@ import { extendedFindParamsMixin } from "../../../../types/common"
  *   - (query) parent_category_id {string} Returns categories scoped by parent
  *   - (query) offset=0 {integer} How many product categories to skip in the result.
  *   - (query) limit=100 {integer} Limit the number of product categories returned.
+ *   - (query) expand {string} (Comma separated) Which fields should be expanded in the product category.
+ *   - (query) fields {string} (Comma separated) Which fields should be included in the product category.
  * x-codeSamples:
  *   - lang: Shell
  *     label: cURL