Rationalize features that are in parquet-format but don't have entry on implementation status

[alamb]

While working on #189 @emkornfield noticed there are several features that are in parquet-format but don't have entry on implementation status: https://github.com/apache/parquet-site/pull/189/changes#r3470611445

Honestly I think most of these are so old, that it doesn't necessary add value, other then maybe providing a note on that page? Is there anything worth surfacing?

Looking more closely, these seem to be the modern ones:

• logical-variant-shredding - should be covered under variant type support? But maybe called out separately
• format-geospatial-statistics - should be covered under geospatial support? But maybe called out separately
• format-binary-protocol-extensions - Not clear if this is actually something on its own without a defined footer we want to use?
• format-ieee-754-total-order-and-nan-counts - This should be added (and we would ideally add a 2026 feature column for read support).

Originally posted by @emkornfield in #189 (comment)

[alamb]

logical-variant-shredding - should be covered under variant type support? But maybe called out separately

Since variant and variant shredding were added at the same time, I think they don't need their own entry

They were added in

• GH-508: Finalize Variant and shredding specs parquet-format#509

[alamb]

I also think geospatial statistics and geospatial support were part of the same PR

The geospatial support and statistics were finalized mainly in one PR:

• parquet-format PR #240: PARQUET-2471: Add GEOMETRY and GEOGRAPHY logical types parquet-format#240

There was a later clarification PR:

• GH-493: Clarify Bounding Box Behavior in GeospatialStatistics  parquet-format#494

On mailing list votes: there was a vote for the original geospatial feature.

• Vote thread: https://lists.apache.org/thread/tgkomrqsynzd5tm3385wm4tfk933lx6w
• PR comment: PARQUET-2471: Add GEOMETRY and GEOGRAPHY logical types parquet-format#240 (comment)