feat(task manager): register info in zk

currently only leader taskmanager registerd in zk. For monitoring, we want query all taskmanager nodes from zk, the same way as nameserver.

Enhance #1232

Impl:
- construct zk path `${zk_root}/taskmanager` as list

The issue mentions enhancing #1232 and constructing a ZooKeeper path `${zk_root}/taskmanager` as a list. Look for existing ZooKeeper registration code for the leader taskmanager and nameserver to understand the pattern. Find where taskmanager nodes are defined and how they connect to ZooKeeper. The goal is to register all taskmanager nodes, not just the leader, for monitoring purposes.

Scritto dal modello di indicizzazione a partire dal testo della issue.