Support ParquetVariant through JNI

[AdamGS]

Summary

This PR builds on top of #8125 to add support for ParquetVariant arrays, as a step towards variant support for Iceberg.

[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.

⚡ 1 improved benchmark
❌ 1 regressed benchmark
✅ 1259 untouched benchmarks

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	chunked_varbinview_opt_canonical_into[(1000, 10)]	224.8 µs	188.1 µs	+19.52%
❌	Simulation	chunked_varbinview_opt_into_canonical[(1000, 10)]	203.8 µs	240.4 µs	-15.22%

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 adamg/parquet-variant-jni (a3f3a76) with adamg/parquet-arrow-import-export (27fbac5)}