hashsum, cksum: Move default stdin to clap

[oech3]

No description provided.

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/tty/tty-eof. tests/tty/tty-eof is passing on 'main'. Maybe you have to rebase?

[RenjiSann]

No need for separated PRs for cksum and hashsum here IMO, can you include the changes in #10042 ? (while keeping 2 separate commits if you prefer)

[oech3]

Done. Yes. we should keep them same.

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/timeout/timeout (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/shuf/shuf-reservoir is no longer failing!
Congrats! The gnu test tests/sort/sort-stale-thread-mem is no longer failing!

[codspeed-hq]

CodSpeed Performance Report

Merging #10043 will degrade performance by 6.56%

_{Comparing oech3:hashsum-stdin-clap (0078c26) with main (44e0bba)}

Summary

❌ 1 regression
✅ 138 untouched
⏩ 37 skipped¹

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	BASE	HEAD	Efficiency
❌	cksum_blake3	210.2 µs	225 µs	-6.56%

Footnotes

1. 37 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. ↩

[oech3]

cksum_blake3 benches the error message given by clap. So it is not a performance regression.

[github-actions]

GNU testsuite comparison:

Congrats! The gnu test tests/shuf/shuf-reservoir is no longer failing!
Congrats! The gnu test tests/sort/sort-stale-thread-mem is no longer failing!