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/models/index-data.ts

@@ -5,6 +5,7 @@ const IndexData = model.define("IndexData", {
   name: model.text().primaryKey(),
   data: model.json().default({}),
   staled_at: model.dateTime().nullable(),
+  // document_tsv: model.tsvector(), NOTE: This is not supported and it is here for reference of its counter part in the migration
 })
 
 export default IndexData