tests(packer): define more common cloud init resources.

tests/cloud-init/debian12-gnome.user-data.yml

@@ -1,45 +1,10 @@
 #cloud-config
 
-packages:
-  - apparmor-profiles
-  - auditd
-  - build-essential
-  - config-package-dev
-  - debhelper
-  - devscripts
-  - htop
-  - qemu-guest-agent
-  - rsync
-  - spice-vdagent
-  - task-gnome-desktop
-  - vim
+packages: *gnome-packages
 
-runcmd:
-  - apt-get update -y
-  - apt-get install -y -t bookworm-backports golang-go
+runcmd: *debian12-runcmd
 
 write_files:
-  # Add backports repository
-  - path: /etc/apt/sources.list
-    append: true
-    content: deb http://deb.debian.org/debian bookworm-backports main contrib non-free
-
-  # Setup shared directory
-  - path: /etc/fstab
-    append: true
-    content: |
-      0a31bc478ef8e2461a4b1cc10a24cc4 /home/user/Projects/apparmor.d  virtiofs defaults  0  1
-
-  # Network configuration
-  - path: /etc/systemd/network/20-wired.network
-    owner: "root:root"
-    permissions: "0644"
-    content: |
-      [Match]
-      Name=en*
-
-      [Network]
-      DHCP=yes
-
-      [DHCPv4]
-      RouteMetric=10
+  - *debian12-backports  # Add backports repository
+  - *shared-directory    # Setup shared directory
+  - *systemd-netword     # Network configuration for server