Updated debianzfs for Debian 12 (Bookworm)

- Shifted release info to packer variables
- Doubled boot_command initial wait to 20s
- Renamed Packer source to debian-live
- Removed .sh from debianzfs script path
- Tweaked comment wording
- Replaced hardcoded codename
- Used 'ln -fs' for existing /etc/mtab

scripts/setup.sh

@@ -1,3 +1,3 @@
 #!/bin/bash
 sudo passwd -d user
-sudo chmod u+x /tmp/debianzfs.sh
+sudo chmod u+x /tmp/debianzfs