Workflow UI replay

# Summary

It would be great if you could scrub a time bar back and forth in the workflow graph view in the argo-server web UI, and view the state of the workflow nodes at different points in time.

# Motivation

Getting a quick feel for what order things happened in, and potentially a more compact way of viewing the workflow through time than the timeline view.

# Proposal

Seems like the necessary data is probably already captured (in etcd or a database) since you can see it in the timeline view. It's a matter of creating the new interface.

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**Message from the maintainers**:

If you wish to see this enhancement implemented please add a 👍 reaction to this issue! We often sort issues this way to know what to prioritize.

Start with the argo-server web UI and inspect how the existing timeline view exposes workflow history and node state. Determine whether the required historical data is available from the current workflow data sources, then define the replay interaction and its acceptance criteria: scrubbing the time bar should show node states at the selected point in time.

Written by the indexing model from the issue text.