Add support for visible time range to the dataframe view

[abey79]

What

• Part of Tracking issue: dataframe view #4466
• Soft-blocked by Use markdown for the view help widget #6878

This adds support for visible time range to the dataframe. For now (likely to be iterated on soon), this mode is enabled when any of the view entities have visible time range enabled (see note below). In that mode, rows are indexed by (entity, time, row_id) and can be sorted with either of the first two (asc or desc) using two new view properties.

The dataframe feature is—and remains—behind an opt-in feature flag.

Note on the current latest at vs. range switch

Currently A single view entity with visible time range force the entire view into this mode. In particular, it force-opt-in all view entities to visible time range, setting it to Rel(0)-Rel(0) when not explicitly set. (It's as if the view's default visible time range switched to Rel(0)-Rel(0) although that's not how it's implemented.)

This implicit behaviour is not ideal, and we probably should design a better way to go about it, see #4466.

Checklist

•  update view help text
• split in multiple files
• clean Chunk stuff
• 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

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[teh-cmc]

Would be nice if we could port this one to the chunk APIs next

[abey79]

ah yes, i ment to do it. I'll do a follow-up PR.