Fix the reindex events, use the sylius resource event to reindex product

[delyriand]

To reindex product, we use sylius events. I keep the event subscriber to reindex data after an update on product positions in taxon.

For the moment, the product delete message doesn't work because we use the product id and in handler the product doen't exist… we should work with the id of the documents to be deleted I think. I create an issue to manage this later