cp: Initial fix to matching GNU coreutils when copying folder that is read only

[jacobgc]

This is my initial attempt at fixing #7961. I'm fairly certain this isn't the correct way of doing this, so I'm very much open to ideas on how I could implement this better

This now produces the exact same output as GNU coreutils tested with:

pushd $(mktemp -d)
mkdir -p a/b/c/d
touch a/b/c/d/bar.txt

chmod -R -w a

cp -r a coreutils
uutils-cp -r a uutils

tree -p a coreutils uutils
popd

It also matches if use the flags --preserve mode and --no-preserve mode. This does not fix the issue when using -a or -p but I plan on looking at that next.

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/cp/existing-perm-dir. tests/cp/existing-perm-dir is passing on 'main'. Maybe you have to rebase?
Skipping an intermittent issue tests/misc/tee (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/cp/existing-perm-dir. tests/cp/existing-perm-dir is passing on 'main'. Maybe you have to rebase?
Skipping an intermittent issue tests/misc/tee (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/timeout/timeout (passes in this run but fails in the 'main' branch)