Improve MethodParameterLookup

[Tim-Pohlmann]

Things to improve in regards to MethodParameterLookup:

• Creation happens via constructors and factory methods, should be stream lined to only factory methods.
• TryGetSyntax takes a IParameterSymbol turns it into a string to then lookup the symbol again. It should be possible to simplify this.
• A string parameterName overload exists for TryGetSyntax but not for TryGetNonParamsSyntax.
• Tests are very hard to extend. Might be worthwhile to change the format.
• It does not support Extension Methods, which would be very useful.