Custom "method signature" code can be replaced with call to IMethodSymbol.ToDisplayString(...)

[simonmckenzie]

I have noticed that while the project has a lot of logic for the generation of method parameters, return types, generic type constraints, etc., the same result can be obtained by using .ToDisplayString(FullyQualifiedDisplayFormat) on the IMethodSymbol.

This means we could delete almost all of this logic and replace it with one line:

https://github.com/codecentric/net_automatic_interface/blob/9d66cad06170853f5b1741573e474f7b6592ee8b/AutomaticInterface/AutomaticInterface/Builder.cs#L100C25-L126C6

... and no doubt similar simplifications could be done for other parts of the interface generation.

What I'm not certain about is whether this is a good idea or not. I've done this replacement locally and all tests pass, but it does mean that it makes later customisation difficult, since all rendering decisions are passed off to Roslyn. Trying to address issues like #62, where the feature request is for something outside what Roslyn offers, would become much harder. Not sure!