Compress fixed-size lists without their null rows

[robert3005]

Add SparseScheme for FixedSizedList. Instead of compressing just the elements we attempt compressing whole lists using SparseArray

Readers need no changes, because Sparse already canonicalizes fixed-size lists.

On the data from #10417:

	Before	After
Mostly-null file (1 row in 20 valid)	25,296 B	9,056 B
Rewrite of both files	292,808 B	190,768 B

[codspeed]

Merging this PR will regress 1 benchmark

⚠️ 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.

⚠️ 12 benchmarks spent significant time in system calls

System calls cannot be consistently instrumented, so they are not included in the measure, which understates the real cost. Please switch to the Walltime instrument to accurately measure system calls.

Measurement and system calls

• decode_primitives[i64, (1000, 32)]
• chunked_dict_primitive_into_canonical[f64, (1000, 1000, 10)]
• filter_run_end[len=4096_run=16_density=0.1]
• multipolygon_mixed_validity
• zstd_compress_string
• ilike_contains
• pcodec_compress_f64
• take_varbin
• decompress[u16, (4000, 256)]
• decompress[u32, (1000, 256)]
• …and 2 more

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 1 improved benchmark
❌ 1 regressed benchmark
✅ 2181 untouched benchmarks
⏩ 359 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	WallTime	bitpack_blocked_compress_avx2	6.8 µs	7.6 µs	-11.65%
⚡ ⚠️	Simulation	decode_primitives[i64, (1000, 32)]	38.4 µs	24.8 µs	+54.85%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing rk/compress-fsl-validity (c05ea8e) with develop (3d12093)²}

Footnotes

1. 359 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on rk/compress-explicit-fallback (c3ad942) during the generation of this report, so develop (3d12093) was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩