feat: Onboard ML datasets

[gkodukula]

Description

pipeline: iris

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Checklist

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• Please merge this PR for me once it is approved.
• If this PR adds or edits a dataset or pipeline, it was reviewed and approved by the Google Cloud Public Datasets team beforehand.
• If this PR adds or edits a dataset or pipeline, I put all my code inside ml_datasets/iris and nothing outside of that directory.
• This PR is appropriately labeled.

[nlarge-google]

Looks Great!