[Enhancement]: terminated and truncated flag, correct use.

[AlejandroCN7]

Improvement 🔧

Recommended by @manjavacas, the flags terminated and truncated should be reformulated in Sinergym in order to be used correctly with SB3 algorithms.

Enhanced behavior

• truncated would be false by default and true when the simulation time limit is reached (what the terminated does right now).
• terminated would be false by default and true when a specific condition happens (to be implemented by the user) is met. For example: deviating N degrees from the comfort limits).

Additional context

For now, mechanisms for early-stopping of episodes under specific conditions will not be implemented. But it is an idea that could be implemented in the future.

Checklist

• [x] I have checked that there is no similar issue in the repo (required)
• [x] I have read the documentation (required)

:pencil: Please, don't forget to include more labels besides enhancement if it is necessary.