opt: propagate null-rejection cols through semi joins

Currently, we do not consider pushing a null-rejecting filter through a semi-join in order to simplify an outer join below it, although we do consider null-rejecting using the filters of the semi-join itself. This leads to cases like in #100559, where an outer-join doesn't get simplified despite a null-rejecting filter because of a semi-join (#100559 also has an internal error for an unrelated reason). We should null-reject columns through semi-joins and maybe also anti-joins.

Jira issue: CRDB-26497