Function cfm_keystore_iterator_next 

#[unsafe(no_mangle)]
pub extern "C" fn cfm_keystore_iterator_next(
    it: *mut FFIKeyIterator,
    out: *mut *mut FFIKey,
) -> u32

Advance the iterator. Returns 0 and writes the next key handle into *out, or Error::ValueNotFound when the iterator is exhausted (in which case *out is left untouched).