cp: ensure --remove-destination doesn't traverse symlinks

cp: ensure --remove-destination doesn't traverse symlinks

* src/cp.c (target_directory_operand): Allow through inaccessible
arguments with -f or --remove.
* doc/coreutils.texi (cp invocation): Clarify that -f doesn't directly
impact the removal of non-traversable symlinks.
* tests/cp/dir-rm-dest.sh: Test the new behavior.
* tests/cp/thru-dangling.sh: Enforce -f behavior wrt symlinks.
* NEWS: Mention the bug fix.
Fixes https://bugs.gnu.org/31335