**Use case**
`SELECT POSITION('/' IN s) FROM (SELECT 'Hello/World' AS s);`

The same as `position(s, '/')`

{
    
    std::string func_name;
    bool trim_left = false;
    bool trim_right = false;
    bool char_override = false;
    ASTPtr expr_node;
    ASTPtr pattern_node;
    ASTPtr to_remove;
    if (ParserKeyword("LTRIM").ignore(pos, expected))
    {
        if (pos->type != TokenType::OpeningRoundBracket)
            return false;
        ++pos;
        trim_left = true;
    }
    else if (ParserKeyword("RTRIM").ignore(pos, expected))
    {
        if (pos->type != TokenType::OpeningRoundBracket)
            return false;
        ++pos;
        trim_right = true;
    }
    else if (ParserKeyword("TRIM").ignore(pos, expected))
    {