printf: avoid overflow for minimum dynamic width

[subotac]

Fixes #13766.

Resolving a negative dynamic width negated the signed argument directly, which overflows for i64::MIN. Use unsigned_abs() so the value reaches the existing width handling safely, and add a regression
test for the minimum signed value.

[codspeed-hq]

Merging this PR will improve performance by 4.54%

⚡ 4 improved benchmarks
✅ 103 untouched benchmarks
⏩ 286 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	ls_recursive_deep_tree[(200, 2)]	3.6 ms	3.4 ms	+5.13%
⚡	Simulation	du_max_depth_balanced_tree[(6, 4, 10)]	63.2 ms	60.4 ms	+4.56%
⚡	Simulation	du_summarize_balanced_tree[(5, 4, 10)]	16.2 ms	15.6 ms	+4.28%
⚡	Simulation	du_wide_tree[(5000, 500)]	20.8 ms	20 ms	+4.2%

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.

---

_{Comparing subotac:fix/printf-min-width-overflow (bdbb205) with main (9f29502)}

Footnotes

1. 286 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. ↩

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/date/resolution (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tail/inotify-dir-recreate (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tail/tail-n0f (fails in this run but passes in the 'main' branch)
Congrats! The gnu test tests/cut/mb-non-utf8 is no longer failing!
Congrats! The gnu test tests/mv/mv-exchange is no longer failing!
Congrats! The gnu test tests/od/od-j is no longer failing!
Congrats! The gnu test tests/dd/no-allocate is now passing!
Note: The gnu test tests/misc/write-errors was skipped on 'main' but is now failing.

[sylvestre]

Please also add a test in test_printf.rs

[sylvestre]

Cf my comment