Make IScope functions typed

[lesquoyb]

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I'm creating this issue mostly to keep track of a discussion with @AlexisDrogoul as it seems like it should be possible to change the methods in IScope (and other core components) that manipulate objects of type Object to generic methods and thus benefit from proper typing.
This is not going to bring more functionalities, but it would make huge parts of the code safer and more readable, removing all the on-the-flight casting and afterward type checking, there's also a small chance that stricter typing could be beneficial in terms of execution time as it should be easier to optimize for the jvm.