Make it possible to log custom components using `rr.send_columns`

[abey79]

What

This PR primarily overhauls rr.AnyBatchValue(), a wrapper around pyarrow to package any data to what looks like a serialised custom component:

• It publicly expose it, including in the python reference documentation.¨
• It makes it compatible with send_columns.
• It add the .partition() method.

Also in this PR:

• Makes rr.AnyValues() compatible with send_columns (you need to call values.as_component_batch() though)
• Add a documentation section to explain all of the above, with a couple of snippets

Checklist

• [x] I have read and agree to Contributor Guide and the Code of Conduct

• [x] I've included a screenshot or gif (if applicable)

• [x] 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

• [x] The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG

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

• [x] If have noted any breaking changes to the log API in CHANGELOG.md and the migration guide

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[github-actions[bot]]

Latest documentation preview deployed successfully.

Result	Commit	Link
✅	51571cefeb4b390c52868041891f73b88b9105f8	https://landing-poek9jfsi-rerun.vercel.app/docs

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[abey79]

@rerun-bot full-check

[github-actions[bot]]

Started a full build: https://github.com/rerun-io/rerun/actions/runs/11859747576