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/utils/src/feature-flags/index.ts

@@ -1,7 +1,9 @@
 export * from "./analytics"
 export * from "./order-editing"
-export * from "./sales-channels"
 export * from "./product-categories"
 export * from "./publishable-api-keys"
+export * from "./sales-channels"
 export * from "./tax-inclusive-pricing"
 export * from "./utils"
+export * from "./workflows"
+