Upgrade to AIP 8.0 simplified

The upgrade to AIP 8.0 when coming from 7.2 and 7.3 has been significantly simplified and all steps are now covered in a new dedicated section of the documentation.

In parallel, the upgrade from AIP 7.0 has also been improved by simplifying the upgrade of the configuration and by removing many steps before and after the upgrade process. This upgrade path now also has e dedicated cookbook.