tests: Rename test scripts, changing - to _ for consistency.

tests/basics/builtin_bin.py

tests/basics/builtin_callable.py

tests/basics/builtin_hex.py

tests/basics/builtin_len1.py

tests/basics/builtin_minmax.py

tests/basics/builtin_oct.py

tests/basics/class_contains.py

tests/basics/class_emptybases.py

tests/basics/class_getattr.py

tests/basics/class_staticclassmethod.py

tests/basics/class_subclass_builtin.py

tests/basics/class_super.py

tests/basics/closure_defargs.py

tests/basics/compare_multi.py

tests/basics/del_attr.py

tests/basics/del_deref.py

tests/basics/del_local.py

tests/basics/del_name.py

tests/basics/del_subscr.py

tests/basics/dict_del.py