Add option to include blueprint in an .rrd when calling .save(…)

[emilk]

What

• Closes Export blueprints for examples and load them from the viewer #5558

This adds an optional blueprint argument to rr.save which if provided, will end up first in the written .rrd file.

When using rr.script_setup (like all our examples do) with a blueprint, --save will put that blueprint in the .rrd file.

This should mean that the examples build by CI will include blueprints.

BONUS: this also adds the blueprint to rr.serve and rr.stdout (and --serve/--stdout in our examples).

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
• If applicable, add a new check to the release checklist!

• PR Build Summary
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[github-actions]

Size changes

Name	main	5572/merge	Change
plots.rrd	0.16 MiB	0.17 MiB	+6.25%