sql: use latest MVCC version for table stat scans

[RaduBerinde]

Pebble optimizes the retrieval of the latest MVCC version for each key. The table statistics scan results in reads that are not for the latest version, which is not ideal.

We should update the scan to not use a timestamp at all, and instead just retrieve the latest version of each key (it is ok to use even a non-committed version). This would be beneficial for the resulting statistics as well.

This will probably require some minor work in KV to allow this type of scan.

CC @jbowens @sumeerbhola

Jira issue: CRDB-57411

[mgartner]

Cool idea! We (SQL Queries) thinks that most of this work would be in KV, so I'm reassigning. Let us know if you disagree.

[RaduBerinde]

Some investigation around this from @annrpom: docs.google.com/document/d/1jItbpNwJUetSQkZwjRgELjDQeCmKvroAep_qN2hLkxg/edit?tab=t.0

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