Rollup merge of #34019 - kennytm:fix-33958, r=steveklabnik

Rollup merge of #34019 - kennytm:fix-33958, r=steveklabnik

Restore original meaning of std::fs::read_dir's example changed in #33958

`DirEntry.file_type().is_dir()` will not follow symlinks, but the original example (`fs::metadata(&path).is_dir()`) does. Therefore the change in #33958 introduced a subtle difference that now it won't enter linked folders. To preserve the same behavior, we use `Path::is_dir()` instead, which does follow symlink.

(See discussion in the previous PR for detail.)