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

**Use case**
People are used to Postgres.
{
    ASTPtr arguments;
    if (!elem_parser->parse(pos, node, expected))
        return false;
    while (true)
    {
        if (!parseOperator(pos, infix, expected))
            break;
        if (!arguments)
        {
            node = makeASTFunction(function_name, node);
            arguments = node->as<ASTFunction &>().arguments;
        }
        ASTPtr elem;
        if (!elem_parser->parse(pos, elem, expected))
            return false;
        arguments->children.push_back(elem);
    }
    return true;
}
bool ParserBetweenExpression::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)