fix: provide useful behavior of default `py::slice` (#5620) * Change behavior of default py::slice * make clang-tidy happy * Update tests/test_pytypes.py --------- Co-authored-by: Bryn Lloyd <12702862+dyollb@users.noreply.github.com> Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>