Migrate variouis test to nspawn container (#523595)

nixos/tests/evcc.nix

@@ -7,7 +7,7 @@ in
   name = "evcc";
   meta.maintainers = with lib.maintainers; [ hexa ];
 
-  nodes = {
+  containers = {
     machine = {
       services.evcc = {
         enable = true;

nixos/tests/pinnwand.nix

@@ -12,7 +12,7 @@ in
     maintainers = [ hexa ];
   };
 
-  nodes = {
+  containers = {
     server =
       { config, ... }:
       {

nixos/tests/postfix-tlspol.nix

@@ -7,7 +7,7 @@
 
   meta.maintainers = with lib.maintainers; [ hexa ];
 
-  nodes.machine = {
+  containers.machine = {
     services.postfix.enable = true;
     services.postfix-tlspol.enable = true;
 

nixos/tests/zigbee2mqtt.nix

@@ -6,7 +6,7 @@
 
 {
   name = "zigbee2mqtt";
-  nodes.machine = {
+  containers.machine = {
     systemd.services.dummy-serial = {
       wantedBy = [
         "multi-user.target"