systemd: use sockets.target

This allows using normal nix-managed services that register sockets for
lazy activation. Also brings in some red errors about starting services
that we don't have, but that will be fixed

nixosModules/default.nix

@@ -72,6 +72,7 @@ in {
       "local-fs.target"
       "nss-user-lookup.target"
       "umount.target"
+      "sockets.target"
       "shutdown.target"
       "reboot.target"
       "exit.target"
@@ -163,6 +164,8 @@ in {
     description = "microVM Application runner";
     onFailure = ["exit.target"];
     onSuccess = ["exit.target"];
+    wants = ["sockets.target"];
+    after = ["sockets.target"];
     wantedBy = ["microvm.target"];
     serviceConfig = {
       Type = "exec";