Add Validity::definitely_all_invalid and use it for AllInvalid fast paths

[joseph-isaacs]

Summary

PR 3 of a 4-PR stack (stacked on #8334) preparing Validity for lazy validity arrays.

Replaces the ~18 scattered matches!(.., Validity::AllInvalid) fast-path checks with a named helper, symmetric with definitely_no_nulls() from #8333. The name makes the conservative semantics explicit: a Validity::Array may still resolve to all-invalid once executed, so false means "unknown without compute", not "definitely has valid values".

Converted sites: the 8 DuckDB exporters, CUDA kernels (fsst, runend, datetime-parts, dynamic dispatch), list_contains, fill_null kernel, primitive top_value, dict codes, masked vtable, and varbin. The three assert!(matches!(...)) sites in tests keep the raw matches!, since they intentionally assert the exact variant.

No behavior change — purely a naming/readability refactor.

Checks

• cargo nextest run -p vortex-array (2962 passed)
• cargo nextest run -p vortex-duckdb (196 passed; test_geometry/over_http excluded — they need network access unavailable in this sandbox)
• cargo clippy -p vortex-array -p vortex-duckdb --all-targets, cargo +nightly fmt --all
• Could not build/test vortex-cuda locally (CUDA toolkit unavailable in this environment).

https://claude.ai/code/session_01VPQ7dfZtijfrsjAipwXvEj

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Generated by Claude Code

[codspeed-hq]

Merging this PR will improve performance by 24.19%

⚠️ 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.

⚡ 5 improved benchmarks
✅ 1527 untouched benchmarks

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	chunked_bool_canonical_into[(1000, 10)]	35.4 µs	20.5 µs	+72.8%
⚡	Simulation	chunked_varbinview_into_canonical[(1000, 10)]	213.1 µs	176.8 µs	+20.53%
⚡	Simulation	bitwise_not_vortex_buffer_mut[128]	244.4 ns	215.3 ns	+13.55%
⚡	Simulation	chunked_varbinview_canonical_into[(100, 100)]	308.4 µs	273.1 µs	+12.94%
⚡	Simulation	bitwise_not_vortex_buffer_mut[1024]	304.7 ns	275.6 ns	+10.58%

Tip

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_{Comparing claude/cool-bardeen-l8jlsy-3-definitely-all-invalid (a13f0ab) with claude/cool-bardeen-l8jlsy-2-mask-eq (3542eaf)}