Method getHelpColumns

tests/catch.hpp:7416–7423

        auto operator+( T const &other ) const -> Parser { return operator|( other ); }

        auto getHelpColumns() const -> std::vector<HelpColumns> {
            std::vector<HelpColumns> cols;
            for (auto const &o : m_options) {
                auto childCols = o.getHelpColumns();
                cols.insert( cols.end(), childCols.begin(), childCols.end() );
            }
            return cols;
        }

        void writeToStream( std::ostream &os ) const {
            if (!m_exeName.name().empty()) {