Add cleanup for private browsing
Rewrite userStorage methods to respect private browsing
Remove unused setCookieFrequency map
Add separate originFrequency store for private sessions
Check private browsing mode in determining disabled sites
Refactor, remove private browsing context in userRed/Yellow/Green

For now, don't keep private stores for userRed/Yellow/Green in private
browsing mode because the cookie permissions manager is not aware of
private browsing anyway.