We support using `typing.Type[]` as a base class (and we have tests for it), but not yet `builtins.type[]`. At some point we should fix that, but I don't think it';s worth spending much time on now (and it might be easier once we've implemented generics?). This PR just adds a failing test with a TODO.
Markdown files within the mdtest/ subdirectory are tests of type inference and type checking;
executed by the tests/mdtest.rs integration test.
See crates/red_knot_test/README.md for documentation of this test format.