Streamline secir python code

[mknaranja]

In https://github.com/SciCompMod/memilio/tree/main/pycode/memilio-simulation/memilio/simulation, the secir model is still named secir.py instead of osecir.py. I do not know how much this deviation of the new style is existent in the code itself.

Could you have a look and maybe directly adapt it @HenrZu @MaxBetzDLR ?

[MaxBetzDLR]

Yes, i can do that. I already found a lot of these deviations and want to go through the whole python simulation package after issues #906 and #761 are merged.

[mknaranja]

@MaxBetzDLR Great. Do you have a rough estimate on how long these PRs still need?