cksum: Adding the functionality for --zero.

[orangeng]

Adding the functionality for --zero / -z. As mentioned in issue #6178

[github-actions[bot]]

GNU testsuite comparison:

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

[sylvestre]

could you please add a test? thanks

[github-actions[bot]]

GNU testsuite comparison:

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

[tertsdiepraam]

Could you check out some of the other utils. I believe we added some functionality for this in uucore. I think it was called LineEnding.

Edit: Here it is: https://docs.rs/uucore/latest/uucore/line_ending/enum.LineEnding.html. It's used in basename for example:

https://github.com/uutils/coreutils/blob/main/src/uu/basename/src/basename.rs#L35

https://github.com/uutils/coreutils/blob/main/src/uu/basename/src/basename.rs#L70-L72

[orangeng]

Changed to use LineEnding. As a general question, is there a good way to know if a needed code function is found in uucore and what is not?

[sylvestre]

is it ready to be reviewed? Thanks

[orangeng]

Unfortunately, school got busy and had to put this aside temporarily. Will be back on this in 1 week.

[RenjiSann]

Ping :) @orangeng Do you have time to finish this ?

[orangeng]

@RenjiSann thanks for reminding me haha, I unfortunately don't have time so I will close this PR. Feel free to have a go at it