Potential bugs for `RUTILS:ITER` 

I [ported](https://github.com/vseloved/rutils/pull/75) a lot of tests from the traditional iter package,  and there are a few potential bugs `RUTILS:ITER` has to tackle with. Please note that the traditional iter also suffers from some [test failures](https://gitlab.common-lisp.net/iterate/iterate/-/issues/23) as well. However, `RUTILS:ITER` has more.