cat: refactor stdio handling

[xtqqczze]

Introduce safe wrappers for raw stdio backed by ManuallyDrop<File>. The ManuallyDrop prevents the file descriptor from being closed on drop, which could otherwise lead to undefined behavior.

The wrapper only exposes &File, so safe code cannot take ownership and accidentally drop the underlying descriptor.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/date/date-locale-hour (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tail/retry (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/rm/isatty (passes in this run but fails in the 'main' branch)

[codspeed-hq]

Merging this PR will not alter performance

✅ 24 untouched benchmarks
⏩ 393 skipped benchmarks¹

---

_{Comparing xtqqczze:dd-stdin-raw (02064e3) with main (e0ff0eb)}

Footnotes

1. 393 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. ↩

[xtqqczze]

Suggested change

	let fd = unsafe { rustix::stdio::take_stdout() };
	let fd = unsafe { OwnedFd::from_raw_fd(libc::STDOUT_FILENO as RawFd) }

We could avoid the rustix dependency here if so desired.

[xtqqczze]

CICD / Build (ubuntu-latest, x86_64-unknown-linux-gnu, feat_os_unix,test_risky_names, use-cross, true) (pull_request) failure tracked by #14251.