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>

integration-tests/modules/src/subscribers/test-event-payload.ts

@@ -0,0 +1,9 @@
+import { SubscriberConfig } from "@medusajs/medusa/src"
+
+const testEventPayloadHandlerMock = jest.fn()
+
+export default testEventPayloadHandlerMock
+
+export const config: SubscriberConfig = {
+  event: "test-event-payload",
+}