feat(medusa, utils): Allow object feature flags (#4701)

Feature flags can be set as follows:

**Environment variables**
```
MEDUSA_FF_ANALYTICS=true
MEDUSA_FF_WORKFLOWS=createProducts,addShippingMethods
```

**Project config**
```
{
  featureFlags: {
    analytics: true,
    workflows: {
      createProducts: true,
      addShippingMethods: true,
    }
  }
}
```

packages/types/src/feature-flag/common.ts

@@ -21,7 +21,7 @@ export interface IFlagRouter {
  */
 export type FeatureFlagsResponse = {
   key: string
-  value: boolean
+  value: boolean | Record<string, boolean>
 }[]
 
 export type FlagSettings = {