Added root and identity parameters for ZooKeeper configuration

Why it matters

This feature was created to allow multiple users to share a single ZooKeeper cluster while maintaining isolation between them. By specifying different root paths and identity settings, users can avoid conflicts and ensure secure, isolated access within the same ZooKeeper environment.

How to use it

In the ZooKeeper configuration for ClickHouse, add the root parameter to specify a unique root path for a user, and the identity parameter to define the identity for that connection. This configuration will isolate user data and operations under different paths and identities on the shared ZooKeeper cluster.