install: implement `--preserve-context`

[Goorzhel]

❯ man install | col -b | grep 'preserve.*context'
       --preserve-context
              preserve SELinux security context

Used in install -C (#1756, coreutils v8.32 ref).

[sylvestre]

I looked at this before and I didn't find a crate to manage SELinux contexts... A simple binding on the library might be enough

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[tertsdiepraam]

Hasn't been fixed yet

[cakebaker]

The issue has been fixed in the meantime with #7908