ls: Implement --zero flag. (#2929)

[pimzero]

Fixes #2929

(Full disclosure, I am very new to rust, and contributing mainly as a learning exercise. But I hope this change can be useful).

This flag can be used to provide a easy machine parseable output from
ls, as discussed in the GNU bug report
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=49716.

There are some peculiarities with this flag:

• Current implementation of GNU ls of the --zero flag implies some
  other flags. Those can be overridden by setting those flags after
  --zero in the command line.
• This flag is not compatible with --dired. This patch is not 100%
  compliant with GNU ls: GNU ls --zero will fail if --dired and
  -l are set, while with this patch only --dired is needed for the
  command to fail.

We also add --dired flag to the parser, with no additional behaviour
change.

Testing done:

$ bash util/build-gnu.sh
 [...]
$ bash util/run-gnu-test.sh tests/ls/zero-option.sh
 [...]
 PASS: tests/ls/zero-option.sh
 ============================================================================
 Testsuite summary for GNU coreutils 9.1.36-8ec11
 ============================================================================
 # TOTAL: 1
 # PASS:  1
 # SKIP:  0
 # XFAIL: 0
 # FAIL:  0
 # XPASS: 0
 # ERROR: 0
 ============================================================================

[sylvestre]

Cool for a first contrib.
Fails on Windows with:

---- test_ls::test_ls_zero stdout ----
current_directory_resolved: 
mkdir: C:\Users\RUNNER~1\AppData\Local\Temp\.tmpVlGog3\0-test-zero
touch: C:\Users\RUNNER~1\AppData\Local\Temp\.tmpVlGog3\1
test-zero
thread 'test_ls::test_ls_zero' panicked at 'called `Result::unwrap()` on an `Err` value: Os { code: 123, kind: Uncategorized, message: "The filename, directory name, or volume label syntax is incorrect." }', tests\common\util.rs:656:40

[pimzero]

Thanks, I suppose this issue is caused by Windows filesystem not supporting newline in filenames, I updated the test to only run with the \n in filenames in unix. Also I fixed the lint & spelling issues the CI found

[sylvestre]

Well done:
Warning: Congrats! The gnu test tests/ls/zero-option is no longer failing!

[tertsdiepraam]

Cool! Nice work on all the edge cases.