Bad implementation of `JsCgVariableConstructor`

[rudolf101]

Description
The JsCgVariableConstructor class was poorly designed and requires significant improvement. At the moment, the super.getOrCreateVariable(model, name) call is used, which can lead to unexpected errors if the source method is changed.

To Reproduce

Compare JsCgVariableConstructor vs PythonCgVariableConstructor vs CgVariableConstructor

Expected behavior

The class uses custom models, similar to how it is done in Python