Add reduce special method to transform wrappers

Summary: Add the ___reduce__ method to transform wrappers (model/generator). This allows transform wrapped objects to be pickled (with original pickle module, not just dill)

Test Plan: tests should pass

Author: JasonKChow

aepsych/transforms/parameters.py

@@ -477,6 +477,10 @@ def eval(self):
                 f"{self._base_obj.__class__.__name__} has no attribute 'eval'"
             )
 
+    def __reduce__(self):
+        # Helps pickle work (not dill)
+        return (ParameterTransformedGenerator, (self._base_obj, self.transforms))
+
     @classmethod
     def get_config_options(
         cls,
@@ -725,6 +729,10 @@ def eval(self):
                 f"{self._base_obj.__class__.__name__} has no attribute 'eval'"
             )
 
+    def __reduce__(self):
+        # Helps pickle work (not dill)
+        return (ParameterTransformedModel, (self._base_obj, self.transforms))
+
     @classmethod
     def get_config_options(
         cls,