Adding unattended upgrades to the pre install script

[3alpha]

Unattended upgrades help keep Debian/Ubuntu systems updated

Testing:

• [x] Running preinstall script on clean Debian install
• [x] Generating ISO and making sure that everything works

[3alpha]

@dsimog01 we need to add here exact same config we are adding to migration.

[pablomendezroyo]

@3alpha 👀