Add back-reference to ZookeeperCluster to Znode discovery CM

[sbernauer]

Currently a ZNode discovery CM looks like shown below. It would be great to have an easy way of retrieving the name + namespace of the underlying zk cluster. This is e.g. needed for affinities

apiVersion: v1                                                                                                                                                                                                                              
data:                                                                                                                                                                                                                                       
  ZOOKEEPER: zookeeper-server-default-0.zookeeper-server-default.default.svc.cluster.local:2282,zookeeper-server-default-1.zookeeper-server-default.default.svc.cluster.local:2282,zookeeper-server-default-2.zookeeper-server-default.defau
lt.svc.cluster.local:2282/znode-d9d46348-caa0-4b8c-aee3-e007fac2e6a4                                                                                                                                                                        
  ZOOKEEPER_CHROOT: /znode-d9d46348-caa0-4b8c-aee3-e007fac2e6a4                                                                                                                                                                             
  ZOOKEEPER_HOSTS: zookeeper-server-default-0.zookeeper-server-default.default.svc.cluster.local:2282,zookeeper-server-default-1.zookeeper-server-default.default.svc.cluster.local:2282,zookeeper-server-default-2.zookeeper-server-default
.default.svc.cluster.local:2282                                                                                                                                                                                                             
kind: ConfigMap                                                                                                                                                                                                                             
metadata:                                                                                                                                                                                                                                   
  creationTimestamp: "2023-02-17T08:02:28Z"                                                                                                                                                                                                 
  labels:                                                                                                                                                                                                                                   
    app.kubernetes.io/component: server                                                                                                                                                                                                     
    app.kubernetes.io/instance: hdfs-znode                                                                                                                                                                                                  
    app.kubernetes.io/managed-by: zookeeper.stackable.tech_znode                                                                                                                                                                            
    app.kubernetes.io/name: zookeeper                                                                                                                                                                                                       
    app.kubernetes.io/role-group: discovery                                                                                                                                                                                                 
    app.kubernetes.io/version: 3.8.0-3.8.0-stackable0.7.1-dns-fix                                                                                                                                                                           
  name: hdfs-znode                                                                                                                                                                                                                          
  namespace: default                                                                                                                                                                                                                        
  ownerReferences:                                                                                                                                                                                                                          
  - apiVersion: zookeeper.stackable.tech/v1alpha1                                                                                                                                                                                           
    controller: true                                                                                                                                                                                                                        
    kind: ZookeeperZnode                                                                                                                                                                                                                    
    name: hdfs-znode                                                                                                                                                                                                                        
    uid: d9d46348-caa0-4b8c-aee3-e007fac2e6a4                                                                                                                                                                                               
  resourceVersion: "31039352518"                                                                                                                                                                                                            
  uid: 6bb938cc-4d71-4d60-99fc-f6b280543bec