[web] Persist userStore in db

Summary:
ENG-7069 : Start performing user store ops on worker
Part of ENG-3490 : Migrate stores to SQLite on web

Start persting userStore on web, inside of sqlite db.

Depends on D11537

Test Plan:

• Open web app, check that the "migration" runs and:
  • Ops with userStore from keyserver are dispatched to the db
  • Redux contains the data
• Reload the web app and check that:
  • Keyserver doesn't send the user info
  • User info is loaded from db and dispatched in setInitialReduxState action
• Play around with the app check if there are any errors
  • Add an unknown user to the friend list
  • Block user
  • Using two clients change the avatar on one and check if it gets synced on the other

Reviewers: kamil, marcin

Reviewed By: kamil

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D11538