Sensitive parameters

# Summary

Add the ability to flag parameters/arguments/variables whether input, or output as sensitive, and ensure that their values don't appear in the UI, CLI, or log output.

# Use Cases

Some operations take in values that are sensitive, or output sensitive values dynamically that would not make sense to be created as a Kubernetes secret. When providing access to the UI to development teams, or less privileged users these values should not be exposed.

I know nothing about the Argo code, but I'm thinking that a boolean `sensitive` field could be added to the `Parameter` object, and be used at the appropriate logging/rendering locations to do the filtering perhaps?

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**Message from the maintainers**:

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Start by tracing the Parameter object and the UI, CLI, and log output paths named in the issue. Determine how input and output values flow through those surfaces; done means values marked sensitive are consistently hidden while ordinary values remain visible.

Written by the indexing model from the issue text.