Manage repositories/select repos to sync in user settings.

Created by: arussellsaw

Feature request description

Once a user has added an access token, but not configured their repos we need to let them choose which repos to sync, as described here: https://www.figma.com/file/zXvqCASHDzmvKbrAl1EVsd/Public-%26-Private-Repos-for-Users-on-Cloud?node-id=700%3A26794

This should reuse a lot of the components from the user repos list, but will require some new graphql connections to get a list of the repos a token can view.