chore: drop the KubeVirt guest bits

The k3s-test workers never ran (they were stuck waiting for volume
binding) and will be re-added as microVMs, so remove their KubeVirt
configs and everything that only existed for KubeVirt guests:

- hosts/k8s/k3s-test-1-worker-{1,2,3} and their outputs
- lib/genKubeVirtGuestModule.nix and lib/genK3sAgentModule.nix (the
  latter was only used by the workers)
- the KubeVirt image upload recipes (upload-vm, upload-idols,
  upload-k3s-test) and the kubevirt image package in the idols outputs
- refresh the docs; keep only accurate historical mentions (e.g. the
  restic backup path must stay as it is)

outputs/x86_64-linux/src/idols-kana.nix

@@ -44,5 +44,4 @@ in
 
   colmena.${name} = mylib.colmenaSystem (systemArgs // { inherit tags ssh-user; });
 
-  packages.${name} = inputs.self.nixosConfigurations.${name}.config.system.build.images.kubevirt;
 }

outputs/x86_64-linux/src/idols-ruby.nix

@@ -44,8 +44,6 @@ in
 
   colmena.${name} = mylib.colmenaSystem (systemArgs // { inherit tags ssh-user; });
 
-  packages.${name} = inputs.self.nixosConfigurations.${name}.config.system.build.images.kubevirt;
-
   # nixos tests
   packages."${name}-nixos-tests" = import ../nixos-tests/idols-ruby.nix systemArgs;
 }

outputs/x86_64-linux/src/k3s-test-1-worker-1.nix

@@ -1,41 +0,0 @@
-{
-  # NOTE: the args not used in this file CAN NOT be removed!
-  # because haumea pass argument lazily,
-  # and these arguments are used in the functions like `mylib.nixosSystem`, `mylib.colmenaSystem`, etc.
-  inputs,
-  lib,
-  mylib,
-  myvars,
-  system,
-  genSpecialArgs,
-  ...
-}@args:
-let
-  name = "k3s-test-1-worker-1";
-  tags = [ name ];
-  ssh-user = "root";
-
-  modules = {
-    nixos-modules =
-      (map mylib.relativeToRoot [
-        # common
-        "secrets/nixos.nix"
-        "modules/nixos/server/server.nix"
-        "modules/nixos/server/qemu-guest-hardware-configuration.nix"
-        # host specific
-        "hosts/k8s/${name}"
-      ])
-      ++ [
-        { modules.secrets.server.kubernetes.enable = true; }
-      ];
-  };
-
-  systemArgs = modules // args;
-in
-{
-  nixosConfigurations.${name} = mylib.nixosSystem systemArgs;
-
-  colmena.${name} = mylib.colmenaSystem (systemArgs // { inherit tags ssh-user; });
-
-  packages.${name} = inputs.self.nixosConfigurations.${name}.config.system.build.images.kubevirt;
-}

outputs/x86_64-linux/src/k3s-test-1-worker-2.nix

@@ -1,41 +0,0 @@
-{
-  # NOTE: the args not used in this file CAN NOT be removed!
-  # because haumea pass argument lazily,
-  # and these arguments are used in the functions like `mylib.nixosSystem`, `mylib.colmenaSystem`, etc.
-  inputs,
-  lib,
-  mylib,
-  myvars,
-  system,
-  genSpecialArgs,
-  ...
-}@args:
-let
-  name = "k3s-test-1-worker-2";
-  tags = [ name ];
-  ssh-user = "root";
-
-  modules = {
-    nixos-modules =
-      (map mylib.relativeToRoot [
-        # common
-        "secrets/nixos.nix"
-        "modules/nixos/server/server.nix"
-        "modules/nixos/server/qemu-guest-hardware-configuration.nix"
-        # host specific
-        "hosts/k8s/${name}"
-      ])
-      ++ [
-        { modules.secrets.server.kubernetes.enable = true; }
-      ];
-  };
-
-  systemArgs = modules // args;
-in
-{
-  nixosConfigurations.${name} = mylib.nixosSystem systemArgs;
-
-  colmena.${name} = mylib.colmenaSystem (systemArgs // { inherit tags ssh-user; });
-
-  packages.${name} = inputs.self.nixosConfigurations.${name}.config.system.build.images.kubevirt;
-}

outputs/x86_64-linux/src/k3s-test-1-worker-3.nix

@@ -1,41 +0,0 @@
-{
-  # NOTE: the args not used in this file CAN NOT be removed!
-  # because haumea pass argument lazily,
-  # and these arguments are used in the functions like `mylib.nixosSystem`, `mylib.colmenaSystem`, etc.
-  inputs,
-  lib,
-  mylib,
-  myvars,
-  system,
-  genSpecialArgs,
-  ...
-}@args:
-let
-  name = "k3s-test-1-worker-3";
-  tags = [ name ];
-  ssh-user = "root";
-
-  modules = {
-    nixos-modules =
-      (map mylib.relativeToRoot [
-        # common
-        "secrets/nixos.nix"
-        "modules/nixos/server/server.nix"
-        "modules/nixos/server/qemu-guest-hardware-configuration.nix"
-        # host specific
-        "hosts/k8s/${name}"
-      ])
-      ++ [
-        { modules.secrets.server.kubernetes.enable = true; }
-      ];
-  };
-
-  systemArgs = modules // args;
-in
-{
-  nixosConfigurations.${name} = mylib.nixosSystem systemArgs;
-
-  colmena.${name} = mylib.colmenaSystem (systemArgs // { inherit tags ssh-user; });
-
-  packages.${name} = inputs.self.nixosConfigurations.${name}.config.system.build.images.kubevirt;
-}