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

**Use case**
People are used to Postgres.
++pos;
        
        if (has_distinct_modifier)
            return false;
        expr_list_params = expr_list_args;
        expr_list_args = nullptr;
        if (distinct.ignore(pos, expected))
            has_distinct_modifier = true;
        if (!contents.parse(pos, expr_list_args, expected))
            return false;
        if (pos->type != TokenType::ClosingRoundBracket)
            return false;
        ++pos;
    }
    auto function_node = std::make_shared<ASTFunction>();
    tryGetIdentifierNameInto(identifier, function_node->name);
    
    if (has_distinct_modifier)
        function_node->name += "Distinct";
    function_node->arguments = expr_list_args;
    function_node->children.push_back(function_node->arguments);
    if (expr_list_params)
    {
        function_node->parameters = expr_list_params;
        function_node->children.push_back(function_node->parameters);
    }
    node = function_node;
    return true;
}
bool ParserCodecDeclarationList::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)