[SPARK-52471] Add Swift-based SparkPi K8s CronJob example

[dongjoon-hyun]

What changes were proposed in this pull request?

This PR aims to add Swift-based SparkPi K8s CronJob example.

Why are the changes needed?

To provide a working example with

• Apache Spark 4.0.0 Connect Server launched by Apache Spark Kubernetes Operator 0.3.0 Helm chart.
• SparkPi Swift App developed with Apache Spark Connect for Swift 0.3.0 library.
• Swift 6.1 language

Does this PR introduce any user-facing change?

No behavior change because this is a new example.

How was this patch tested?

Manual tests.

# Install Spark K8s Operator
$ helm install spark spark/spark-kubernetes-operator

# Launch Spark 4.0 Connect Server
$ kubectl apply -f examples/spark-connect-server.yaml

# Launch `Swift-based SparkPi` Application
$ kubectl  apply -f examples/job/cron-pi-swift.yaml

$ kubectl get cronjob
NAME                     SCHEDULE    TIMEZONE   SUSPEND   ACTIVE   LAST SCHEDULE   AGE
spark-connect-swift-pi   * * * * *   <none>     False     1        2s              7m51s

$ kubectl get pod -l job-name
NAME                                    READY   STATUS      RESTARTS   AGE
spark-connect-swift-pi-29163859-mkh5p   0/1     Completed   0          2m31s
spark-connect-swift-pi-29163860-btc66   0/1     Completed   0          91s
spark-connect-swift-pi-29163861-68mmt   0/1     Completed   0          31s

Was this patch authored or co-authored using generative AI tooling?

No.

[dongjoon-hyun]

Thank you, @viirya .

[dongjoon-hyun]

Merged to main.