[SPARK-52827] Add pi-with-template.yaml example

[dongjoon-hyun]

What changes were proposed in this pull request?

This PR aims to add pi-with-template.yaml example to illustrate podTemplateSpec in addition to the docs.

Why are the changes needed?

This is frequently used to specify priorityClassName and other K8s spec like the following.

  driverSpec:
    podTemplateSpec:
      spec:
        priorityClassName: system-cluster-critical
        terminationGracePeriodSeconds: 0
  executorSpec:
    podTemplateSpec:
      spec:
        priorityClassName: system-cluster-critical
        terminationGracePeriodSeconds: 0

Does this PR introduce any user-facing change?

No.

How was this patch tested?

Manually test.

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

No.

[dongjoon-hyun]

cc @peter-toth

[dongjoon-hyun]

Thank you, @viirya . Merged to main.

[peter-toth]

Late LGTM.