Improve getMasterURL() to add [] to IPv6 if needed

[LittleWat]

Resolves #1344

Spark 3.4 supports IPv6:

• [SPARK-39468][CORE] Improve RpcAddress to add [] to IPv6 if needed apache/spark#36868

So I want to make the operator also support IPv6.

I can confirm that this can submit the following spark job that uses spark 3.4 both in IPv6-only and IPv4 environments.
(Although it is necessary to add the following environment variables to the operator in the IPv6-only environment... for the workaround of the okhttp3 bug

• Move to use okhttp4 due to a bug on IPV6 based cluster fabric8io/kubernetes-client#2632 )

apiVersion: apps/v1
kind: Deployment
metadata:
  name: spark-on-k8s-spark-operator
spec:
  template:
    spec:
      containers:
      - name: spark-operator
        env:
        - name: _JAVA_OPTIONS
          value: "-Djava.net.preferIPv6Addresses=true"
        - name: KUBERNETES_DISABLE_HOSTNAME_VERIFICATION
          value: "true"

The sample I tested:

apiVersion: sparkoperator.k8s.io/v1beta2
kind: SparkApplication
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"sparkoperator.k8s.io/v1beta2","kind":"SparkApplication","metadata":{"annotations":{},"name":"spark-pi","namespace":"data-platform-demo"},"spec":{"driver":{"coreLimit":"1200m","cores":1,"labels":{"version":"3.4.1"},"memory":"512m","serviceAccount":"spark"},"executor":{"cores":1,"instances":1,"labels":{"version":"3.4.1"},"memory":"512m"},"image":"apache/spark:3.4.1","imagePullPolicy":"Always","mainApplicationFile":"local:///opt/spark/examples/jars/spark-examples_2.12-3.4.1.jar","mainClass":"org.apache.spark.examples.SparkPi","mode":"cluster","restartPolicy":{"type":"Never"},"sparkVersion":"3.4.1","type":"Scala"}}
  creationTimestamp: "2023-08-31T05:19:57Z"
  generation: 5
  name: spark-pi
  namespace: data-platform-demo
  resourceVersion: "219867269"
  uid: fcfc6341-e0df-4679-a1cb-e0983f3a8423
spec:
  driver:
    coreLimit: 1200m
    cores: 1
    labels:
      version: 3.4.1
    memory: 512m
    serviceAccount: spark
  executor:
    cores: 1
    instances: 1
    labels:
      version: 3.4.1
    memory: 512m
  image: apache/spark:3.4.1
  imagePullPolicy: Always
  mainApplicationFile: local:///opt/spark/examples/jars/spark-examples_2.12-3.4.1.jar
  mainClass: org.apache.spark.examples.SparkPi
  mode: cluster
  restartPolicy:
    type: Never
  sparkVersion: 3.4.1
  type: Scala
status:
  applicationState:
    state: COMPLETED
  driverInfo:
    podName: spark-pi-driver
    webUIAddress: fd85:464b:2e72::f610:0
    webUIPort: 4040
    webUIServiceName: spark-pi-ui-svc
  executionAttempts: 1
  executorState:
    spark-pi-88a60e8a4a219c23-exec-1: COMPLETED
  lastSubmissionAttemptTime: "2023-08-31T05:47:00Z"
  sparkApplicationId: spark-c0bd0af55802492494682041bbdd22d5
  submissionAttempts: 1
  submissionID: 329a09b9-139a-4e55-b034-c7ebeda9e82e
  terminationTime: "2023-08-31T05:47:23Z"