Teach zoned pruning to lower StatFn

[gatesn]

Summary

• lower StatFn-based pruning predicates over zoned stats instead of the legacy StatsCatalog path
• map null/NaN pruning aggregates to existing NullCount/NaNCount zone stats plus row_count
• remove the old zoned pruning fallback to checked_pruning_expr

Tests

• cargo test -p vortex-array stats::rewrite::builtins
• cargo test -p vortex-array all_nan
• cargo test -p vortex-array all_non_nan
• cargo test -p vortex-layout zone_map
• cargo test -p vortex-layout -- --test-threads=1
• cargo clippy -p vortex-array --all-targets --all-features
• cargo clippy -p vortex-layout --all-targets --all-features
• ./scripts/public-api.sh
• git diff --check

[codspeed-hq]

Merging this PR will not alter performance

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

✅ 1216 untouched benchmarks

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_{Comparing ngates/stats-7707/zoned-statfn-pruning (096128a) with ngates/stats-7707/built-in-rewrite-rules (ad61595)}