text: Title: mc_dropout with predict_likelihood_parameters
  Body: Hi, thanks for the prompt response regarding issue #2097 . I'm now able to utilize `mc_dropout` in `historical_forecasts`. 
  
  My current objective is to incorporate `mc_dropout` for obtaining epistemic uncertainty and `predict_likelihood_parameters` for acquiring aleatoric uncertainty. However, when setting `predict_likelihood_parameters` to `True`, I encounter an issue where I'm unable to use the sample method. Consequently, I'm limited to obtaining only one result with each call to `historical_forecasts` with `predict_likelihood_parameters=True` and `mc_dropout=True`.
  
  I suspect that the solution might involve distinguishing the sample generation process by using mc_dropout and sample generation process based on the fitted distribution. Now they are using the same `num_samples` parameter.