Redirect pre-8.0 stable users to a separate update directory
In order to achieve watershed for the ESR60 switch, we should redirect pre-8.0 stable users to a separate update directory, using the option added in #26234 (moved), so that they are updated to 8.0 first before being updated to the latest version.
This ticket is similar to #26569 (moved), but for the release
channel.
We should do this after 8.0
has been released.