CSVLookupTableMixin: Also cache the CasADi function
This function can be very costly to regenerate. For NZV, it can easily take 30 seconds. Because SXFunctions can be cached, we can also just cache this function to save a lot of time.
This function can be very costly to regenerate. For NZV, it can easily take 30 seconds. Because SXFunctions can be cached, we can also just cache this function to save a lot of time.