feat(uucore): support fs feature for redox

[xtqqczze]

The fs feature now compiles successfully on Redox:

cargo clippy --quiet --package uucore --features=fs --all-targets --target=x86_64-unknown-redox

Closes #14704

[codspeed]

Merging this PR will degrade performance by 27.2%

⚠️ 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 improved benchmarks
❌ 1 regressed benchmark
✅ 331 untouched benchmarks
⏩ 117 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	three_39_bit_primes	302.4 ms	967.6 ms	-68.74%
⚡	Simulation	true_consecutive_calls	350.2 ns	294.7 ns	+18.85%
⚡	Simulation	thirteen_39_bit_primes	9 s	8.7 s	+3.87%

Tip

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

---

_{Comparing xtqqczze:redox-create-link-std (06a4f23) with main (154be8e)²}

Footnotes

1. 117 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. ↩

2. No successful run was found on main (a7f2dc5) during the generation of this report, so 154be8e was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/date/resolution (passes in this run but fails in the 'main' branch)

[cakebaker]

Thanks!