Add buffered printing and lock output stream to tsort

[mrkalling]

This pull request adds buffered output and locks stdout during printing to improve performance. As a side effect, tsort no longer panics when printing to stdout fails.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/tail/tail-n0f (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/misc/io-errors (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/tail/retry (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/dd/no-allocate is now passing!
Congrats! The gnu test tests/pr/bounded-memory is now passing!

[codspeed-hq]

Merging this PR will improve performance by 12.07%

⚠️ 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

⚡ 4 improved benchmarks
✅ 319 untouched benchmarks
⏩ 46 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	tsort_tree_dag[(10, 3)]	29.1 ms	25.3 ms	+15.16%
⚡	Simulation	tsort_wide_dag[100000]	115.9 ms	102.4 ms	+13.23%
⚡	Simulation	tsort_linear_chain[1000000]	1.4 s	1.3 s	+10.34%
⚡	Simulation	tsort_complex_dag[50000]	73.2 ms	66.8 ms	+9.65%

Tip

Curious why this is faster? Comment @codspeedbot explain why this is faster on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing mrkalling:martink (78b6f7e) with main (8243543)}

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. ↩

[sylvestre]

please ping instead of doing rebase, it isn't helpful :(