Add --stdout/-o to our CLI helper library

[teh-cmc]

You can now pipe all Python & Rust examples into a Rerun Viewer.

Checks:

• python examples/python/minimal_options/main.py -o | rerun -
• cargo r -p minimal_options -- -o | rerun -

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I have tested the web demo (if applicable):
  • Using newly built examples: app.rerun.io
  • Using examples from latest main build: app.rerun.io
  • Using full set of examples from nightly build: app.rerun.io
• The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG

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