generator: conditional parentheses should support more than 1 parenthesis

[tahini]

For example a condition that would be C1 && (c2 || (c3 && c4)) requires close 2 parentheses at the end, but we get this error in the integrity check: Error in Conditionals sheet - Invalid parentheses in row 97: must be one of ['(', ')'] or empty, got '))'. In this specific case, operation priority makes it possible to bypass this limitation, but more complex cases may arise that would require more than one opening/closing parentheses.

[samuel-duhaime]

@tahini Yes, you are right, but I'm pretty sure that the main problem is not the validation message, but that the current function will break with this calculation.
Right now, it can only handle single parentheses, not double or more. We will need to fix it before updating the message for this case.

[tahini]

Of course, this issue includes the whole support of multiple parentheses, not just the error message ;-)