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,
    }
  }
}
```

integration-tests/plugins/medusa-config.js

@@ -1,4 +1,5 @@
 const { Modules } = require("@medusajs/modules-sdk")
+const { Workflows } = require("@medusajs/workflows")
 const DB_HOST = process.env.DB_HOST
 const DB_USERNAME = process.env.DB_USERNAME
 const DB_PASSWORD = process.env.DB_PASSWORD
@@ -31,6 +32,11 @@ module.exports = {
     cookie_secret: "test",
     database_extra: { idle_in_transaction_session_timeout: 0 },
   },
+  featureFlags: {
+    workflows: {
+      [Workflows.CreateProducts]: true,
+    },
+  },
   modules: {
     [Modules.STOCK_LOCATION]: {
       scope: "internal",