chore(): revert route loading parallelization (medusajs#14204)

**What**
To prevent undeterministic route loading, remove route loading concurrency

Author: adrien2p

.changeset/dull-pots-dream.md

@@ -0,0 +1,5 @@
+---
+"@medusajs/framework": patch
+---
+
+chore(): revert route loading parallelization

packages/core/framework/src/http/router.ts

@@ -1,4 +1,4 @@
-import { ContainerRegistrationKeys, parseCorsOrigins, promiseAll } from "@medusajs/utils"
+import { ContainerRegistrationKeys, parseCorsOrigins } from "@medusajs/utils"
 import cors, { CorsOptions } from "cors"
 import type { ErrorRequestHandler, Express, RequestHandler } from "express"
 import type {
@@ -85,12 +85,10 @@ export class ApiLoader {
     const routesLoader = new RoutesLoader()
     const middlewareLoader = new MiddlewareFileLoader()
 
-    await promiseAll(
-      this.#sourceDirs.flatMap(dir => [
-        routesLoader.scanDir(dir),
-        middlewareLoader.scanDir(dir)
-      ])
-    )
+    for (const dir of this.#sourceDirs) {
+      await routesLoader.scanDir(dir)
+      await middlewareLoader.scanDir(dir)
+    }
 
     return {
       routes: routesLoader.getRoutes(),