feat(utils): define file config (#13283)

** What
 - Allow auto-loaded Medusa files to export a config object.
 - Currently supports isDisabled to control loading.
 - new instance `FeatureFlag` exported by `@medusajs/framework/utils`
 - `feature-flags` is now a supported folder for medusa projects, modules, providers and plugins. They will be loaded and added to `FeatureFlag`

** Why
 - Enables conditional loading of routes, migrations, jobs, subscribers, workflows, and other files based on feature flags.

```ts
// /src/feature-flags

import { FlagSettings } from "@medusajs/framework/feature-flags"

const CustomFeatureFlag: FlagSettings = {
  key: "custom_feature",
  default_val: false,
  env_key: "FF_MY_CUSTOM_FEATURE",
  description: "Enable xyz",
}

export default CustomFeatureFlag
```

```ts
// /src/modules/my-custom-module/migration/Migration20250822135845.ts

import { FeatureFlag } from "@medusajs/framework/utils"

export class Migration20250822135845 extends Migration {
  override async up(){ }
  override async down(){ }
}

defineFileConfig({
  isDisabled: () => !FeatureFlag.isFeatureEnabled("custom_feature")
})
```

packages/medusa-test-utils/src/module-test-runner.ts

@@ -27,6 +27,7 @@ function createMikroOrmWrapper(options: {
   moduleModels?: (Function | DmlEntity<any, any>)[]
   resolve?: string
   dbConfig: any
+  cwd?: string
 }): {
   MikroOrmWrapper: TestDatabase
   models: (Function | DmlEntity<any, any>)[]
@@ -36,7 +37,7 @@ function createMikroOrmWrapper(options: {
 
   if (!options.moduleModels) {
     const basePath = normalizeImportPathWithSource(
-      options.resolve ?? process.cwd()
+      options.resolve ?? options.cwd ?? process.cwd()
     )
 
     const modelsPath = fs.existsSync(`${basePath}/dist/models`)
@@ -74,6 +75,7 @@ export function moduleIntegrationTestRunner<TService = any>({
   testSuite,
   resolve,
   injectedDependencies = {},
+  cwd,
 }: {
   moduleName: string
   moduleModels?: any[]
@@ -85,6 +87,7 @@ export function moduleIntegrationTestRunner<TService = any>({
   injectedDependencies?: Record<string, any>
   resolve?: string
   debug?: boolean
+  cwd?: string
   testSuite: (options: SuiteOptions<TService>) => void
 }) {
   const moduleSdkImports = require("@medusajs/framework/modules-sdk")
@@ -107,6 +110,7 @@ export function moduleIntegrationTestRunner<TService = any>({
     moduleModels,
     resolve,
     dbConfig,
+    cwd,
   })
 
   moduleModels = models
@@ -135,6 +139,7 @@ export function moduleIntegrationTestRunner<TService = any>({
     databaseConfig: dbConfig,
     joinerConfig,
     preventConnectionDestroyWarning: true,
+    cwd,
   }
 
   let shutdown: () => Promise<void>