Do not generate, instantiate, nor carry Arrow extensions around

[teh-cmc]

• Do not generate, instantiate, nor carry Arrow extensions around: we do not need them, ever. We rely on chunk metadata for everything meta-esque.
• Do not let datatypes pretend that they have semantics. They do not need names.
• Clean everything accordingly.

---

• DNM: requires Never direct users towards using rr.log_components #8151

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 examples from latest main build: rerun.io/viewer
  • Using full set of examples from nightly build: rerun.io/viewer
• 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!
• If have noted any breaking changes to the log API in CHANGELOG.md and the migration guide

• PR Build Summary
• Recent benchmark results
• Wasm size tracking

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[teh-cmc]

@rerun-bot full-check

[github-actions]

Started a full build: https://github.com/rerun-io/rerun/actions/runs/11842783240

[abey79]

"Feel good PR of the year" contender. Changes looks rather straightforward too 👍🏻