feat(medusa): Rollout index engine behind feature flag (#11431)

**What**
- Add index engine feature flag
- apply it to the `store/products` end point as well as `admin/products`
- Query builder various fixes
- search capabilities on full data of every entities. The `q` search will be applied to all involved joined table for selection/where clauses

Co-authored-by: Carlos R. L. Rodrigues <37986729+carlos-r-l-rodrigues@users.noreply.github.com>

packages/modules/index/src/utils/default-schema.ts

@@ -4,14 +4,24 @@ export const defaultSchema = `
   type Product @Listeners(values: ["${Modules.PRODUCT}.product.created", "${Modules.PRODUCT}.product.updated", "${Modules.PRODUCT}.product.deleted"]) {
     id: String
     title: String
+    handle: String
+    status: String
+    type_id: String
+    collection_id: String
+    is_giftcard: String
+    external_id: String
+    created_at: DateTime
+    updated_at: DateTime
+
     variants: [ProductVariant]
     sales_channels: [SalesChannel]
   }
-  
+
   type ProductVariant @Listeners(values: ["${Modules.PRODUCT}.product-variant.created", "${Modules.PRODUCT}.product-variant.updated", "${Modules.PRODUCT}.product-variant.deleted"]) {
     id: String
     product_id: String
     sku: String
+
     prices: [Price]
   }