Let feature_extractor and extract_fluents callable being resettable.

[marcofavorito]

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

TemporalGoalWrapper.feature_extractor and TemporalGoal.extract_fluents are of type callable.

It is possible to create extractor that depends on more than one state, by keeping memory of the past states:

class my_feature_extractor:
    
    def __init__(self, *args, *kwargs):
        ...

    # this method makes the class callable
    def __call__(self, obs, action):
        ...

wrapper = TemporalGoalWrapper(env, feature_extractor=my_feature_extractor(), ...)

however, the state of the extractor is kept across episodes.

Describe the solution you'd like

TemporalGoalWrapper should call a reset() method of feature_extractor and of every extract_fluents. Of course they might not have a method called reset(), in that case just skip them.

Describe alternatives you've considered

Additional context