Update:

1. expose is_exist, create_dir, copy, rename, remove, stat, list.
   Now it only remains reader, writer, lister.
2. add valgrind in test ci to check more memory leak occasion
3. add docs-only option to avoid install dependency in docs ci

About Operator::read, I changed impl in #2984 because address sanitizer outputs container overflow. But I found that this is a misinformation caused by missing sanitize option for libopendal_cpp. As result, I revert previous impl. However, we still can't avoid copy because all std::vector pointer constructor use copy to hide internal structure.