`INTERVAL '1 hour'` should be equivalent to `INTERVAL 1 HOUR`

**Use case**
People are used to Postgres.
nulls_direction_was_explicitly_specified = true;
        if (first.ignore(pos))
            nulls_direction = -direction;
        else if (last.ignore(pos))
            ;
        else
            return false;
    }
    ASTPtr locale_node;
    if (collate.ignore(pos))
    {
        if (!collate_locale_parser.parse(pos, locale_node, expected))
            return false;
    }
    
    bool has_with_fill = false;
    ASTPtr fill_from;
    ASTPtr fill_to;
    ASTPtr fill_step;
    if (with_fill.ignore(pos))
    {
        has_with_fill = true;
        if (from.ignore(pos) && !exp_parser.parse(pos, fill_from, expected))
            return false;
        if (to.ignore(pos) && !exp_parser.parse(pos, fill_to, expected))
            return false;
        if (step.ignore(pos) && !exp_parser.parse(pos, fill_step, expected))
            return false;
    }
    node = std::make_shared<ASTOrderByElement>(