Revert "remove rbtree_delete_node_back"

This reverts commit 0a602d81583f7531faa9b8f7438c3ca48e9d8345.
Revert "Revert "remove rbtree_delete_node_back""

This reverts commit 9fb9fba56036515e096c64320a3d8b0cfeda9ac2.
Revert "Revert "Revert "remove rbtree_delete_node_back"""

This reverts commit c54a90a0c0e04b25b043d7315d1d379f6212dc87.