bootctl: print SystemdOptions from efivarfs if newer than our cache

bootctl: print SystemdOptions from efivarfs if newer than our cache

The logic is that if the options are updated after boot, we *don't* use
the new value. But we still want to print out the changed contents in
bootctl as to not confuse people.

Fixes #19597.
Also https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=988450.

$ build/bootctl systemd-efi-options
quiet
Note: SystemdOptions EFI variable has been modified since boot. New value: debug

The hint is printed to stderr, so scripts should not be confused.