fix(truncate): implement --io-blocks

[ThomasHabets]

Scale SIZE by the preferred I/O block size of each output file, using the parent filesystem for files that do not exist yet.

Before

truncate --io-blocks --size=1 file produced a 1-byte file.

After

The same command produces a 4096-byte file on a filesystem with 4096-byte I/O blocks.

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/rm/isatty (passes in this run but fails in the 'main' branch)
Note: The gnu test tests/rm/many-dir-entries-vs-OOM is now being skipped but was previously passing.

[codspeed-hq]

Merging this PR will not alter performance

✅ 339 untouched benchmarks
⏩ 46 skipped benchmarks¹

---

_{Comparing ThomasHabets:truncate-blocks (d6e060f) with main (ef50d8b)}

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. ↩

[Copilot]

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[sylvestre]

Looks good

[ThomasHabets]

Not sure what this means. Is it a false positive? I seem to be rebased correctly on top of HEAD

REGRESSIONS (non-intermittent failures):
Error: GNU test failed: tests/dd/misc. tests/dd/misc is passing on 'main'. Maybe you have to rebase?
Error: GNU test failed: tests/df/over-mount-device. tests/df/over-mount-device is passing on 'main'. Maybe you have to rebase?

[cakebaker]

@ThomasHabets yes, it's a false positive.

[cakebaker]

Thanks!