Add labels to K8S Workflow events

# Summary
It would be very useful to add labels to Workflow controller events, such as WorkflowSucceeded WorkflowFailed, including a label pointing back to the CronWorkflow object (if the Workflow is a child Node of a CWF).

# Use Cases
This would be used with Argo Events / ResourceEventSource when we need to listen on successful / failed completion events of a CronWorkflow.

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**Message from the maintainers**:

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Start by tracing where Workflow controller events such as WorkflowSucceeded and WorkflowFailed are emitted, then inspect how a Workflow identifies a parent CronWorkflow. The work is complete when these events carry labels and child Workflows include a label pointing to their CronWorkflow, with behavior verified for successful and failed completion events.

Written by the indexing model from the issue text.