At this point all of the custom final_message is now obsolete.
Remove it, letting us instead use the default final_message.
Leave a note about the above.
- drop ds-identify policy, not needed with improved cloud config
- drop disabling network, doesn't work with ip=
- fixup setting up the INSTALLER_ROOT mountpoint
- enable cloud-init
- make cloud-init handle the default/baked in networking configuration
- install and enable openssh-server for the installation only
- provide cloud.cfg that generates random installer user password
- disable subiquity on sclp_line0 line based console