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

**Use case**
People are used to Postgres.
{
    
    
    ASTPtr expr_node;
    ASTPtr type_node;
    if (ParserKeyword("CAST").ignore(pos, expected)
        && ParserToken(TokenType::OpeningRoundBracket).ignore(pos, expected)
        && ParserExpression().parse(pos, expr_node, expected)
        && ParserKeyword("AS").ignore(pos, expected)
        && ParserDataType().parse(pos, type_node, expected)
        && ParserToken(TokenType::ClosingRoundBracket).ignore(pos, expected))
    {
        
        auto type_literal = std::make_shared<ASTLiteral>(queryToString(type_node));
        auto expr_list_args = std::make_shared<ASTExpressionList>();
        expr_list_args->children.push_back(expr_node);
        expr_list_args->children.push_back(std::move(type_literal));
        auto func_node = std::make_shared<ASTFunction>();
        func_node->name = "CAST";
        func_node->arguments = std::move(expr_list_args);
        func_node->children.push_back(func_node->arguments);
        node = std::move(func_node);
        return true;
    }
    return false;
}
bool ParserSubstringExpression::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)