Tracking Issue: Retire the legacy statistics APIs #10177

Epic: #10175

This tracking issue is for the migration from the old legacy fixed statistics APIs to aggregate functions in vortex-array, file summaries, downstream integrations, and compressor callers.

Design

Replace runtime ArrayStats, StatsSet, and fixed Stat APIs with aggregate requests keyed by the full function and options.

Historical node hints, footer fields, and legacy zone summaries will have to remain readable through compatibility adapters/converters, with fixed field identifiers confined to those adapters.

Steps

• Replace the runtime array cache API and migrate compute and encoding consumers.
• Migrate footer summaries, pruning, and downstream metadata consumers.
• Migrate remaining fixed-stat callers in compression.
• Preserve historical metadata compatibility and document the Rust API migration.

Implementation history

• Centralize aggregate stat bridge #7931 connected aggregates to the legacy array cache.
• Use aggregate descriptors for zoned stats #7938 migrated zoned summaries to aggregate descriptors and partial states.
• Rework AggregateVTable #9816 clarified typed partial-state contracts.