nixos/lib/test-driver: add driver-timeout as a passthru test

From now on, we will aim to ensure that the test driver
gets tested by OfBorg using all our available tests.

This commit adds the driver timeout test to the driver.

nixos/lib/test-driver/default.nix

···
 , tesseract4
 , vde2
 , extraPythonPackages ? (_ : [])
+, nixosTests
 }:
 
 python3Packages.buildPythonApplication {
···
   ]
     ++ (lib.optionals enableOCR [ imagemagick_light tesseract4 ])
     ++ extraPythonPackages python3Packages;
+
+  passthru.tests = {
+    inherit (nixosTests.nixos-test-driver) driver-timeout;
+  };
 
   doCheck = true;
   nativeCheckInputs = with python3Packages; [ mypy ruff black ];