fix: Add _bare-metal suffix for False boolean modifiers to prevent filename collisions

The manifest uses hyphenated keys (guest-agents, hardware-support) but the filename
generation was looking for underscored keys, causing 16 variants to overwrite 4 files.

Added _get_modifier() helper to normalize both key formats and added _bare-metal suffix
for False values of guest_agents, ensuring unique filenames for all variant combinations.

This restores the intended 24 distinct variants from the manifest and adds support for
all modifiers (bootloader, initial-setup, desktop, security, storage, guest_agents, hardware_support).

dishes/install_virtual_hypervisor-desktop_amdcpu_43.cfg

@@ -14,6 +14,8 @@ lang en_US.UTF-8
 network  --bootproto=dhcp --device=link --hostname=phyllome-alpha --activate
 # Shutdown after installation
 shutdown
+repo --name="fedora" --mirrorlist=https://mirrors.fedoraproject.org/mirrorlist?repo=fedora-43&arch=x86_64
+repo --name="updates" --mirrorlist=https://mirrors.fedoraproject.org/mirrorlist?repo=updates-released-f43&arch=x86_64
 #Root password
 rootpw --lock
 # SELinux configuration
@@ -22,6 +24,8 @@ selinux --enforcing
 services --enabled="NetworkManager,systemd-resolved"
 # System timezone
 timezone Europe/Zurich --utc
+# Use network installation
+url --mirrorlist="https://mirrors.fedoraproject.org/mirrorlist?repo=fedora-43&arch=x86_64"
 # X Window System configuration information
 xconfig  --defaultdesktop=GNOME --startxonboot
 # System bootloader configuration