Separate LXC, VM and microvm configs (it's getting ugly, need to tidy things up soon)

systems/microvm.nix

@@ -1,9 +1,9 @@
 { inputs, lib, config, microvm, ... }:
 let
-  cfg = config.services.vm;
+  cfg = config.services.micro_vm;
 in
 {
-  options.services.vm = {
+  options.services.micro_vm = {
     enable = lib.mkEnableOption "Enable NixOS microvm config";
     hostname = lib.mkOption {
       type = lib.types.str;