feat: restructure events payload (#8143)

* refactor: restructure events payload

Breaking change: This PR changes the event payload accepted by the event
listeners

* refactor: fix failing tests and implement feedback

* add integration tests

* fix timeout

---------

Co-authored-by: Adrien de Peretti <adrien.deperetti@gmail.com>

packages/medusa/src/loaders/helpers/subscribers/index.ts

@@ -1,7 +1,7 @@
 import {
+  Event,
   IEventBusModuleService,
   MedusaContainer,
-  MessageBody,
   Subscriber,
 } from "@medusajs/types"
 import { kebabCase, ModuleRegistrationName } from "@medusajs/utils"
@@ -193,10 +193,9 @@ export class SubscriberLoader {
     const subscriberId = this.inferIdentifier(fileName, config, handler)
 
     for (const e of events) {
-      const subscriber = async (data: MessageBody<T>) => {
+      const subscriber = async (data: T) => {
         return await handler({
-          eventName: e,
-          data,
+          event: { name: e, ...data } as unknown as Event<T>,
           container: this.container_,
           pluginOptions: this.pluginOptions_,
         })