printf: avoid panic on large numeric field widths

[Air-crypto]

Fixes #13850.

Write numeric field padding in bounded chunks instead of passing widths above u16::MAX to Rust's formatting machinery. This prevents %65536d from panicking and adds a regression test for the expected 65,536-byte output.

Tests passed:

• cargo test --no-default-features --features printf test_printf::
• cargo test -p uucore
• cargo clippy --no-default-features --features printf --all-targets -- -D warnings
• cargo fmt --all -- --check

[github-actions]

Binary size comparison:

Individual binary size comparison VS main (threshold: >=5% AND >=4 KB).

Total size of compared binaries: 148.93 MB (+316 KB, +0.21%)

Significant per-binary changes:
  install     1.24 MB ->    1.32 MB  (+80 KB, +6.29%)
  mkdir       1.09 MB ->    1.17 MB  (+80 KB, +7.14%)
  mkfifo      1.09 MB ->    1.16 MB  (+76 KB, +6.83%)
  mknod       1.09 MB ->    1.17 MB  (+76 KB, +6.79%)

[sylvestre]

please document why 1024

[sylvestre]

Lgtm if the ci is happy

[codspeed-hq]

Merging this PR will degrade performance by 18.61%

⚠️ 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

❌ 1 regressed benchmark
✅ 346 untouched benchmarks
⏩ 46 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	df_with_path	573.7 µs	704.9 µs	-18.61%

Tip

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

---

_{Comparing Air-crypto:air-crypto/prinft-large-field-width-fix (bc89833) with main (822aa83)}

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. ↩

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/cut/bounded-memory (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/date/date-locale-hour (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/date/resolution (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/tail/symlink (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/tail/pipe-f2 is no longer failing!
Note: The gnu test tests/seq/seq-epipe is now being skipped but was previously passing.