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,
    }
  }
}
```

.changeset/loud-wombats-shave.md

@@ -0,0 +1,7 @@
+---
+"@medusajs/medusa": patch
+"@medusajs/types": patch
+"@medusajs/utils": patch
+---
+
+feat(medusa, utils): Allow object feature flags