Implement lazy-loading for products data

[pkarw]

What is the motivation for adding / enhancing this feature?

Currently, when user enters product page or category we're downloading pretty heavy data file including all product infromation - category-next/storeproduct/actions:cacheProducts is being called. In CSR it's even 2 requests - first is for simplified JSON file; second is executed just to cache all the products in browser memory and the feed in the Service Worker

This sucks on slow 3g connections.

We should have a configurable data fetching strategy to save the bandwidth. We should keep VSF as it is and have config.api.saveBandwidthOverCache=false default option. If it's true - then we shouldn't cache products and categories but rather limit the set of fields being used for getting the data; launching network call each time user is entering product page to get just this product info (probably we can also limit the number of fields being retrieved a little bit)

This is kind of R&D task