Fix sync all/select all logic for the welcome + manage repos views
Created by: artemruts
Description
Fixes sync all/select all repositories problems that we encountered during the E2E tests.
Additionally:
- makes sure we don't equate "sync all current, and future repositories with "all individual repositories are selected"
- in the welcome flow, when the current step is not complete - users can't navigate to any of the steps to the right
Edit: "Sync all" feature is disabled again but is ready whenever we want to introduce this feature again.