(Low priority) Move nwf from CPPProcess.cc to CPPProcess.h in cudacpp?

[valassi]

(This is a followup to #644 and a possible improvement for the solution in MR #560)

Hi @nscottnichols thanks for your comment #671 (comment)

IIUC it should be possible to move nwf from CPPProcess.cc to CPPProcess.h by properly controlling the order of function calls in the python code generation. I agree, as I initially was not even able to include nwf in CPPProcess.cc, and I only later realised that I had to call the python functions in some specific order.

I file this as a future reminder, but for the moment it is low priority. As the nwf is moved out of src and into P1, the functional issues are now solved, even if nwf os in CPPProcess.cc. I agree however that it would be nicer to have it in CPPProcess.h, which is also the case of npar in #667

Thanks again Nathan!