test(tail): fix flaky test_follow_name_multiple on macOS

[naoNao89]

Fixes CI: #9587 #9632

Fixes flaky test_follow_name_multiple by increasing timeout from 500ms to 3000ms on macOS.

Root cause: macOS FS caching delays output visibility when test framework reads redirected temp files.

for i in {1..5}; do echo "=== Run $i ==="; cargo test --test tests test_tail::test_follow_name_multiple -- --nocapture 2>&1 |grep -A 2 "test test_tail::test_follow_name_multiple"; done
=== Run 1 ===
test test_tail::test_follow_name_multiple ... FAILED

failures:

failures:
    test_tail::test_follow_name_multiple
=== Run 2 ===
test test_tail::test_follow_name_multiple ... FAILED

failures:

failures:
    test_tail::test_follow_name_multiple
=== Run 3 ===
test test_tail::test_follow_name_multiple ... FAILED

failures:

failures:
    test_tail::test_follow_name_multiple
=== Run 4 ===
test test_tail::test_follow_name_multiple ... FAILED

failures:

failures:
    test_tail::test_follow_name_multiple
=== Run 5 ===
test test_tail::test_follow_name_multiple ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 3691 filtered out; finished in 7.61s

https://github.com/uutils/coreutils/actions/runs/20132879326/job/57778876765 https://github.com/uutils/coreutils/actions/runs/20113818498/job/57718649405?pr=9629

[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #9636 will degrade performances by 3.24%

_{Comparing naoNao89:fix/tail-follow-name-multiple-files (e02607d) with main (415d01c)[^unexpected-base]} [^unexpected-base]: No successful run was found on main (4a1b969) during the generation of this report, so 415d01c was used instead as the comparison base. There might be some changes unrelated to this pull request in this report.

Summary

⚡ 1 improvement
❌ 3 regressions
✅ 123 untouched
⏩ 6 skipped[^skipped]

:warning: Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
❌	sort_numeric	23.2 ms	24 ms	-3.24%
⚡	mv_multiple_to_dir	13.1 ms	12.9 ms	+2.05%
❌	unexpand_large_file[10]	549.3 ms	562.8 ms	-2.4%
❌	unexpand_many_lines[100000]	262 ms	268.4 ms	-2.4%
[^skipped]: 6 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[bot]]

GNU testsuite comparison:

Skip an intermittent issue tests/tail/overlay-headers (fails in this run but passes in the 'main' branch)

[github-actions[bot]]

GNU testsuite comparison:

Skipping an intermittent issue tests/tail/overlay-headers (passes in this run but fails in the 'main' branch)