Dataframe v2: support for clear semantics

[teh-cmc]

Support clear semantics in the dataframe API.
Tombstones are never visible to end-users, only their effect.

Like every other Dataframe v2 feature PR, and following recommendations from @jleibs, this prioritizes convenience of implementation over everything else, for now.
All clear chunks are fetched, post-processed, and re-injected into the view contents during init(), and then the streaming join runs as usual after that.

Static clear semantics can get pretty unhinged, but that's A) not specific to the dataframe API and B) so extremely niche that our time is better spent on real-world problems right now:

• Static Clear semantics are under-defined and very confusing #7650
• re_query recursive clear checks are incorrect #7631

---

• Fixes Expand rust APIs to support new Data API concepts #7495
• Fixes Dataframe API should expose mechanism to return sorted results. #7414
• Fixes Timeline and Clear handling issues in dataframe range queries #7468
• Fixes Tombstone data should not be returned by default in high-level dataframe APIs #7493
• DNM: requires Dataframe v2: new and improved chunk tools #7649

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[jleibs]

Nice. I like this partitioning. Makes it easier to cache/optimize fetch_clear_chunks in the future with some additional data-structures + the component-refactoring we've discussed.

[github-actions]

Deployed docs

Commit	Link
5f92358	https://landing-4xjs9140y-rerun.vercel.app/docs