tsort stdout flushing fix and several error messages handling ameliorations

[anastygnome]

fixes #14383
fixes #12006
closes #12065

The HEAD tsort added buffering but did not check whether writing was successful or not. I
I added the fix and modified the locale to make the names use generic constants.

[codspeed-hq]

Merging this PR will regress 1 benchmark

⚡ 1 improved benchmark
❌ 1 regressed benchmark
✅ 365 untouched benchmarks
⏩ 50 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	mv_directory	8.2 ms	8.5 ms	-3.57%
⚡	Simulation	mv_force_overwrite	177.9 ms	148 ms	+20.24%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

---

_{Comparing anastygnome:tsort (62bf93f) with main (9ff4114)}

Footnotes

1. 50 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. ↩

[anastygnome]

welp, bench seemed like they had a cache issue on their test machine? The perf reg is in the allocator for IntVec

[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/tail/tail-n0f (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/tail/pipe-f is now passing!

[anastygnome]

@sylvestre
@cakebaker

this is good to merge, and should asap, currently all write errors are gobbled.

[anastygnome]

I agree your solution is better in terms of error management, I have autosquashed the commit and put us both as coauthors :)

[anastygnome]

The CI failure is unrelated

[xtqqczze]

CICD / Build (ubuntu-latest, x86_64-unknown-linux-musl, feat_os_unix_musl, use-cross) (pull_request) tracked by #14251.