Serialize table managers in save_principal_table_to_list

[saiashok0981]

GitHub PR Description

### Summary
This PR implements serialization of `table_managers` in `acl_principal_table::save_principal_table_to_list` in `acl.cc`.

### Proposed Changes
- Iterates over `managers_` (up to `num_managers_`) and calls `pl->add_table_managers(managers_[j])` to ensure managers are saved to the protobuf message.
- Replaces the `// Todo: add managers` comment with the actual implementation.