Generate model from discrete env

[marcofavorito]

Is your feature request related to a problem? Please describe.

In case the wrapped environment is DiscreteEnv, the wrapper forgets the model.

Describe the solution you'd like
Make TemporalGoalWrapper able to detect if the wrapped environment is an instance of DiscreteEnv, and in that case, extend the model such that the automata transitions are included.

Describe alternatives you've considered
n/a

Additional context
n/a