[SPARK-50758][K8S]Mounts the krb5 config map on the executor pod

[maomaodev]

What changes were proposed in this pull request?

In this pr, for spark on k8s, the krb5.conf config map will be mounted in executor side as well.
Before, the krb5.conf config map is only mounted in driver side. But according to the parameter description, the krb5.conf file should be mounted on both the driver and the executor.

  val KUBERNETES_KERBEROS_KRB5_FILE =
    ConfigBuilder("spark.kubernetes.kerberos.krb5.path")
      .doc("Specify the local location of the krb5.conf file to be mounted on the driver " +
        "and executors for Kerberos. Note: The KDC defined needs to be " +
        "visible from inside the containers ")
      .version("3.0.0")
      .stringConf
      .createOptional

  val KUBERNETES_KERBEROS_KRB5_CONFIG_MAP =
    ConfigBuilder("spark.kubernetes.kerberos.krb5.configMapName")
      .doc("Specify the name of the ConfigMap, containing the krb5.conf file, to be mounted " +
        "on the driver and executors for Kerberos. Note: The KDC defined" +
        "needs to be visible from inside the containers ")
      .version("3.0.0")
      .stringConf
      .createOptional

Why are the changes needed?

After SPARK-43504, the hadoop config map will be mounted on the executor pod.
Now the executor pod fails to start because the hadoop conf file contains Kerberos authentication configuration, but the executor does not mount krb5.conf correctly.
See the #41181 discuss.

Does this PR introduce any user-facing change?

Yes, users do not need to take workarounds to make executors load the krb5.conf.
Such as:

• including krb5.conf in executor image
• placing krb5.conf in executor working directory using --files

How was this patch tested?

UT.
Authored-by: lifumao [email protected]