Use Eigen::Ref<> ?

[olilarkin]

I haven't properly checked if this is the case here, but using Eigen types as function parameters can result in unwanted temporary copies in some cases. The Eigen::Ref<> class exists to work around this. Further information here: http://eigen.tuxfamily.org/dox/TopicFunctionTakingEigenTypes.html#TopicUsingRefClass

I wondered if this might be one lever for optimizing the NAMCore code

https://github.com/sdatkinson/NeuralAmpModelerCore/blob/885a535d29022138f3efcbfd73aed4743f750b68/NAM/wavenet.h#L102C6-L102C6