feat: Update the product options model and refactor the product module (#6685)

The changes in this PR are:
1. Change how product options are created and stored. The relationship changed from
`options --> option values <-- variants`
to
`options --> option values --> variant options <-- variants`

Now we can enforce non-duplicate option values, easier creation and updates of options, and more.

2. Refactors the product module. The product module did a lot of things in a non-ideal approach, and this is a step towards a more consistent usage of the base repository and methods exposed by a module. There is still work left to improve the module, but a large chunk of the changes are included in this PR


Things to do as a follow-up:
1. Remove many-to-many relationships  if an empty list is passed in the base repository.
2. Improve the typings of the module
3. Further cleanup and improvements (there are few questions that I need answered before I can improve the API)

integration-tests/factories/simple-product-variant-factory.ts

@@ -34,7 +34,7 @@ export const simpleProductVariantFactory = async (
 
   const id = data.id || `simple-variant-${Math.random() * 1000}`
 
-  const toSave = manager.create(ProductVariant, {
+  const toSave = await manager.create(ProductVariant, {
     id,
     product_id: data.product_id,
     sku: data.sku,