unwrap internal uint8array from RkyvWriter

[cometkim]

No description provided.

[codspeed-hq]

Merging this PR will degrade performance by 12.17%

❌ 1 regressed benchmark
✅ 59 untouched benchmarks
⏩ 82 skipped benchmarks¹

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	complex/encode - Order (large)	1.5 ms	1.7 ms	-12.17%

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_{Comparing writer-unwrap-uint8array (b5ae53e) with main (2c3fc14)}

Footnotes

1. 82 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. ↩