Save lift tests to InferenceData

[wd60622]

This would be required to rebuild same model after using lift test methods.

Currently missing:

• save the lift tests to the fit_data group
• upon load, add the lift tests to the model likelihood
  • Would be done here

An alternative to this would be to save the lift test to a separate group. However, this would likely cause some additional complexity and would have to capture additional warnings. The fit_data just runs the risk of having to change the structure of the fit_data group itself and likely have to have a version bump of the model.

[wd60622]

The kwargs used with the would have to be saved off as well or the reconstructed model would not be the same https://github.com/pymc-labs/pymc-marketing/blob/4bddf9450f7a85ade4a03ccb47af55bcefc4b982/pymc_marketing/mmm/delayed_saturated_mmm.py#L1735-L1740

Potentially these kwargs in the attrs like in the save and load methods. This seems to require that each df_lift_test would have to be saved in separate variable? Maybe using another group like lift_tests would be more clear?