chore: Initialize method for modules (#3649)

What:
- Export initialize methods for all modules to be used as a package.
- Export `runMigrations` and `revertMigration` on modules that DB migrations are available

```typescript
import {
  initialize as initializeInventory,
  InventoryServiceInitializeOptions,
  runMigrations as runMigrationsInventory,
} from "@medusajs/inventory";

import { initialize as eventBusInitialize } from "@medusajs/event-bus-redis";

import { initialize as cacheInitialize } from "@medusajs/cache-redis";

const eventBus = await eventBusInitialize({
  redisUrl: "localhost",
});

const cache = await cacheInitialize({
  redisUrl: "localhost",
});

const options: InventoryServiceInitializeOptions = {
  database: {
    type: "postgres",
    url: `postgres://postgres:@localhost/inventory`,
  },
};

await runMigrationsInventory({
  options,
});

const inventoryService = await initializeInventory(options, {
  eventBusService: eventBus,
});

const sku = "sku_123"
const item = await service.createInventoryItem({
  sku,
});

cache.set(sku, { item });

```

packages/inventory/src/initialize/index.ts

@@ -2,17 +2,18 @@ import {
   ExternalModuleDeclaration,
   InternalModuleDeclaration,
   MedusaModule,
+  Modules,
 } from "@medusajs/modules-sdk"
 import { IEventBusService, IInventoryService } from "@medusajs/types"
 import { InventoryServiceInitializeOptions } from "../types"
 
 export const initialize = async (
-  options?: InventoryServiceInitializeOptions | ExternalModuleDeclaration,
+  options: InventoryServiceInitializeOptions | ExternalModuleDeclaration,
   injectedDependencies?: {
     eventBusService: IEventBusService
   }
 ): Promise<IInventoryService> => {
-  const serviceKey = "inventoryService"
+  const serviceKey = Modules.INVENTORY
   const loaded = await MedusaModule.bootstrap(
     serviceKey,
     "@medusajs/inventory",