Export VarBin to Arrow without canonicalizing the encoding first

[robert3005]

to_arrow_byte_array used a private ArrowByteExportable matcher listing VarBin, Chunked and Constant. That list is closed, so an encoding such as FSST, OnPair or Zstd was executed all the way to a canonical VarBinView, and the builder then had to re-lay out every value the encoding could have written directly.

It now stops at dyn VarBinExportable, so operators like Filter and Slice still run (and push down) while the encoding underneath them keeps its specialized append_to_builder, and out-of-crate encodings participate by claiming the capability.

Alongside the dynamic export target we fix the validation of null values (required by arrow) and redundant casting of offsets

[codspeed-hq]

Merging this PR will improve performance by 15.45%

⚡ 2 improved benchmarks
✅ 1960 untouched benchmarks
🆕 4 new benchmarks
⏩ 89 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	cold_misaligned[(64, 256)]	5.2 ms	4.4 ms	+19.31%
⚡	Simulation	slice_primitive_tight_loop[10000]	473.8 µs	424.1 µs	+11.71%
🆕	Simulation	file_to_offset_array[binary_array]	N/A	317.6 ms	N/A
🆕	Simulation	file_to_offset_array[string_array]	N/A	317.6 ms	N/A
🆕	Simulation	file_to_offset_batches[binary_array]	N/A	195.6 ms	N/A
🆕	Simulation	file_to_offset_batches[string_array]	N/A	196.1 ms	N/A

Tip

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_{Comparing rk/arrowvarbinnoexecute (a39053c) with develop (ca7f626)²}

Footnotes

1. 89 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/string-arrow-benches (4fce0bc) during the generation of this report, so develop (ca7f626) was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩