clippy: fix str_to_string lint

[xtqqczze]

https://rust-lang.github.io/rust-clippy/master/index.html#str_to_string

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/tty/tty-eof (fails in this run but passes in the 'main' branch)
Note: The gnu test tests/dd/no-allocate is now being skipped but was previously passing.

[github-actions]

GNU testsuite comparison:

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

[nyurik]

just fyi - i tried running it from my local clippy clone (on main) -- cargo dev lint <full-path-to-coreutils> -- --fix --allow-dirty --workspace --all-features after adding str_to_string = "warn" to Cargo.toml - tons of changes. Note that I ran it on top of my other PR, so your changes might be different. That said, I think it is better to merge #10704 first - otherwise it will have tons of conflicts, and my PR already had tons of manual work, whereas running the above fix command would do it automatically.

[codspeed-hq]

Merging this PR will not alter performance

✅ 284 untouched benchmarks
⏩ 38 skipped benchmarks¹

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_{Comparing xtqqczze:clippy/str_to_string (f33e12d) with main (398e4ba)}

Footnotes

1. 38 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:

Congrats! The gnu test tests/basenc/bounded-memory is now passing!

[github-actions]

GNU testsuite comparison:

Congrats! The gnu test tests/basenc/bounded-memory is now passing!