Add possibility to pass an Operation to update method of Variable

[scastd]

Describe the feature

Add a new method in the Variable class that allows to pass an Operation as parameter:

void update(Operation<T> operation);

So the usages can be like this:

vars.<Integer>get("varName").update(Operations.add(1));

Additional information

• [x] Would you be willing to help implement this feature?

Final checks

• [X] Read the contribution guide.
• [X] Check existing discussions and issues.