chown: -h on symlink to directory operates on link, not target

[rossilor95]

Fixes #11887

chown -h on a symlink-to-directory chowned the target instead of the link. The Linux fast path used Path::is_dir(), which resolves symlinks and routed the call into the directory-traversal branch.

Switch to Metadata::is_dir() on the already-lstat'd metadata so the --no-dereference contract is preserved. Added regression test test_chown_no_dereference_symlink_to_dir that creates a symlink to a directory, runs chown --no-dereference, and asserts via ctime that the syscall touched the symlink's inode (link's ctime advances) and not the target's (directory's ctime is unchanged). Confirmed the test fails on the unfixed code and passes with the fix.

Repro (from #11887)

$ chown -h nobody root                 # symlink: root -> /root
$ ls -ld /root root
drwx------ nobody root  /root          # ← bug: target chowned
lrwxrwxrwx root   root  root -> /root  # ← bug: link untouched

# GNU does the opposite
$ gnuchown -h nobody root
drwx------ root   root  /root
lrwxrwxrwx nobody root  root -> /root

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/cut/bounded-memory (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/date/date-locale-hour (fails in this run but passes in the 'main' branch)

[sylvestre]

some jobs are failing

[rossilor95]

some jobs are failing

I solved the style issue (my bad, forgot to run cargo fmt before committing 😅).

About Open BSD/Tests, seems to be failing with the same error for at least another PR, error: linking with cc failed: exit status: 1. Any ideas?

[xtqqczze]

test_chown_no_dereference_symlink_to_dir was failing on merge: https://github.com/uutils/coreutils/actions/runs/26679895315/job/78638347716#step:3:6091