fix(spark): reject MapType instead of emitting a childless Arrow List

[jackylee-ch]

SparkToArrowSchema mapped MapType to a childless ArrowType.List, which is an invalid Arrow list (a List must have exactly one child). Drop the branch so MapType falls through to the existing fail-fast UnsupportedOperationException, and add a test.

[codspeed-hq]

Merging this PR will improve performance by 11.17%

⚡ 1 improved benchmark
✅ 1669 untouched benchmarks
⏩ 52 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	true_count_vortex_buffer[128]	580.6 ns	522.2 ns	+11.17%

Tip

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_{Comparing jackylee-ch:spark-schema-map-fail-fast (1e47bbc) with develop (3975895)}

Footnotes

1. 52 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. ↩