AddParens only if it is not already a ParenthesizedExpressionSyntax

[LucTremblay]

Enhancement

#1146

Using the test RelationalOperatorsOnNullableTypeInConditionAsync for demonstration

During the debugging session:

For vb node (with nullable variable) at the begining of ConvertBinaryExpressionAsync method :
x = y

C# code at the end of the method:
Before:
ParenthesizedExpressionSyntax ParenthesizedExpression ((((((((x))).HasValue)&&((((y))).HasValue)))&&((((((x))).Value)==((((y))).Value)))))

After:
ParenthesizedExpressionSyntax ParenthesizedExpression ((((x).HasValue)&&((y).HasValue))&&(((x).Value)==((y).Value)))

Solution

In AddParens, only add parenthesis if it is not already a ParenthesizedExpressionSyntax
This eliminate a lot of unneeded parenthesis

This is a modification to the current AddParens method. It seems to have only one definition of such method. But the SyntaxFactory.ParenthesizedExpression is directly call at many place in the code.