Upgrade a Landscape 19.10 Juju installation to Landscape 23.03

It is advisable to perform the upgrade steps associated with the manual upgrade with the Juju instances. The upgrade journey will resemble a backup and restore, as opposed to an in-place upgrade, because the underlying operating system in each Juju instance is being upgraded from Ubuntu 18.04 to either Ubuntu 20.04 or Ubuntu 22.04.