dd: fix stdout output

[zhw2101024]

Fixes #11557
Added DdError since io::Result as return type is not enough for this fix.
Many changes to pass the clippy checks, please tell me if there's better solutions.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/date/date-locale-hour (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/cut/bounded-memory (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/pr/bounded-memory (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/tail/tail-n0f (passes in this run but fails in the 'main' branch)

[oech3]

We don't aim generating 100% same error message with GNU. But exit code should be same and should not panic.

[zhw2101024]

Hello, are there more concerns about this change?

[codspeed-hq]

Merging this PR will degrade performance by 3.98%

⚠️ 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

❌ 2 regressed benchmarks
✅ 343 untouched benchmarks
⏩ 46 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	cksum_default	38.2 ms	39.8 ms	-4.02%
❌	Simulation	cksum_multiple_files	58.3 ms	60.7 ms	-3.95%

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 zhw2101024:fix_stdout_output (8b4c801) with main (37b1d11)}

Footnotes

1. 46 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. ↩