Add `tasks.<TASKNAME>.podName` to DAG Templates

# Summary

Add `tasks..podName` to DAG Templates

Add `steps..podName` to Steps Templates

## Use Cases

1. The default key for artifact is `{{workflow.name}}/{{pod.name}}/< NAME >`. If it is added, then this key can be concatenated in other tasks.
2. other tasks need read pod name of previous task

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**Message from the maintainers**:

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The issue names no files or tests; start by locating how DAG and Steps templates expose task fields and how template variables are tested. Done means both task.podName and step.podName are available to other tasks for the stated artifact and dependency use cases.

Written by the indexing model from the issue text.