inventory tests: use containers by default

lib/test/container-test-driver/test-script-prepend.py

@@ -0,0 +1,9 @@
+# This file contains type hints that can be prepended to Nix test scripts so they can be type
+# checked.
+
+from collections.abc import Callable
+
+from test_driver import Machine
+
+start_all: Callable[[], None]
+machines: list[Machine]