nixos/tests: fix tests that use SDDM (#436705)

nixos/tests/lxqt.nix

···
       with subtest("Wait for login"):
           machine.wait_for_x()
           machine.wait_for_file("/tmp/xauth_*")
+          machine.sleep(1)
           machine.succeed("xauth merge /tmp/xauth_*")
           machine.succeed("su - ${user.name} -c 'xauth merge /tmp/xauth_*'")
 

nixos/tests/maestral.nix

···
 
       with subtest("GUI"):
         gui.wait_for_x()
-        gui.wait_for_file("/tmp/xauth_*")
-        gui.succeed("xauth merge /tmp/xauth_*")
+        gui.wait_for_file("/run/user/1000/xauth_*")
+        gui.sleep(1)
+        gui.succeed("xauth merge /run/user/1000/xauth_*")
         gui.wait_for_window("^Desktop ")
         gui.wait_for_unit("maestral.service", "${user.name}")
     '';

nixos/tests/plasma6.nix

···
     ''
       with subtest("Wait for login"):
           start_all()
-          machine.wait_for_file("/tmp/xauth_*")
-          machine.succeed("xauth merge /tmp/xauth_*")
+          machine.wait_for_file("/run/user/1000/xauth_*")
+          machine.sleep(1)
+          machine.succeed("xauth merge /run/user/1000/xauth_*")
+          machine.succeed("su - ${user.name} -c 'xauth merge /run/user/1000/xauth_*'")
 
       with subtest("Check plasmashell started"):
           machine.wait_until_succeeds("pgrep plasmashell")
···
 
       with subtest("Ensure Elisa is not installed"):
           machine.fail("which elisa")
-
-      machine.succeed("su - ${user.name} -c 'xauth merge /tmp/xauth_*'")
 
       with subtest("Run Dolphin"):
           machine.execute("su - ${user.name} -c 'DISPLAY=:0.0 dolphin >&2 &'")

nixos/tests/retroarch.nix

···
         enable = true;
         package = pkgs.retroarch-bare;
       };
-      services.xserver.displayManager = {
+      services.displayManager = {
         sddm.enable = true;
         defaultSession = "RetroArch";
         autoLogin = {
···
   testScript =
     { nodes, ... }:
     let
-      user = nodes.machine.config.users.users.alice;
+      user = nodes.machine.users.users.alice;
       xdo = "${pkgs.xdotool}/bin/xdotool";
     in
     ''
       with subtest("Wait for login"):
           start_all()
-          machine.wait_for_file("/tmp/xauth_*")
-          machine.succeed("xauth merge /tmp/xauth_*")
+          machine.wait_for_file("/run/sddm/xauth_*")
+          machine.sleep(1)
+          machine.succeed("xauth merge /run/sddm/xauth_*")
 
       with subtest("Check RetroArch started"):
           machine.wait_until_succeeds("pgrep retroarch")

nixos/tests/sddm.nix

···
         machine.screenshot("sddm")
         machine.send_chars("${user.password}\n")
         machine.wait_for_file("/tmp/xauth_*")
+        machine.sleep(1)
         machine.succeed("xauth merge /tmp/xauth_*")
         machine.wait_for_window("^IceWM ")
       '';
···
       testScript = ''
         start_all()
         machine.wait_for_file("/tmp/xauth_*")
+        machine.sleep(1)
         machine.succeed("xauth merge /tmp/xauth_*")
         machine.wait_for_window("^IceWM ")
       '';