feat: change state to userdict

[younesStrittmatter]

Description

Change state into a user dict

• resolves when creating new state, make it more convenient to add fields to the state. It's inconvenient now because you have to create a new state class. autora#548

Type of change

• feat: A new feature

• BREAKING_CHANGE: Not sure if it breaks existing code, but tests/notebooks in the core worked fine

Remarks (Optional)

• The old state class is still implemented and State, StandardState are now aliases of the "Dict"-Versions. If we find Problems, we can easily go back to the Dataclass solution
• The advantage of this is, that the fields of the state can now be changed dynamically. For example, one can add fields easily and alter their "delta"-behaviour between cycles

[musslick]

This looks great! The only suggestion I have is to add a minimal jupyter notebook under docs/cycle that outlines the new functionality, i.e., how the state can be modified (adding fields, changing delta functions).

[musslick]

Looks great!

[hollandjg]

I think this needs a bunch of automated tests before it gets merged — it's such a central part of the core, that we really need confidence it's working!

[hollandjg]

I think this class would benefit from a bunch of doctests which demo and check it's full functionality! You could start with the doctests in the StandardState as an example, and then add the new functionality too.