ENG-3490 : Migrate stores to SQLite on web
Now that we have will start persisting message store in sqlite on web, we need to have a redux transform, like on native which will split data between persited by redux and persisted by sqlite. This diff moves the transform to lib (+ updated comments). The transformer will be added to web in the later diffs.

Depends on D11536

Check if the app on native works. Check if rehydrated store contains data from both sources.