feat(sdk): Use display_name for Kubernetes pod names

[wassimbensalem]

Summary

Enables set_display_name() to affect Kubernetes pod names for container tasks, improving cluster-side debugging and resource monitoring.

Benefits

• Easier debugging: Pod names match display names, simplifying task identification in kubectl, logs, and monitoring tools
• Resource monitoring: In ParallelFor loops, each iteration's pod has a clear name, enabling per-component resource usage tracking
• Better observability: Metrics and logs can be easily correlated with pipeline tasks

Changes

• pipeline_task.py: Enhanced set_display_name() to handle LoopArgumentVariable objects from ParallelFor loops
• pipeline_spec_builder.py:
  • Use sanitized display_name as DAG task key for container tasks
  • Fix producer task references in groups (ParallelFor, Condition, ExitHandler) to use correct DAG keys
  • Ensure uniqueness and enforce Kubernetes naming constraints

Features

• Display names are sanitized and used for pod names
• Supports loop variables: task.set_display_name(f"task-{loop_var.field}")
• Handles duplicate names with automatic suffix
• Truncates to fit Kubernetes 63-char limit
• Fully backward compatible

Fixes

• Resolves "unknown producer task" error when using display_name in groups

Testing

• Added unit tests for display_name functionality
• Tested with ParallelFor loops
• Verified backward compatibility

Related

Closes #12434

[google-oss-prow]

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[google-oss-prow]

Hi @wassimbensalem. Thanks for your PR.

I'm waiting for a kubeflow member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[droctothorpe]

/ok-to-test