Refactor models

[flo-dup]

Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

Does this PR already have an issue describing the problem ?
Related to #113 and fixes #114

What kind of change does this PR introduce?
Refactor

What is the current behavior? (You can also link to an open issue here)

• Each model corresponds to a BlackBoxModel
• All models in same package
• staticId, parameterSetId might be empty strings

What is the new behavior (if this is a feature change)?

• A model corresponds to a BlackBoxModel only if it's modelled as such in dynawo, that is, only if it's written in the dyd file.
  Therefore the default network models do not implement the BlackBoxModel interface. A Model interface has been introduced above BlackBoxModel to model those default models.
• Reorganize class architecture: each type of equipment has its own package. In each package there might be default network models together with BlackBoxModels.
• Adding class VarMapping with parameters dynamicVariable and staticVariable instead of Pair<String, String>
• Adding class VarConnection with parameters var1 and var2 instead of Pair<String, String>
• Delete BlackBoxEventModel (duplicate of BlackBoxModel)
• StaticId is optional

Does this PR introduce a breaking change or deprecate an API? yes

• The Breaking Change or Deprecated label has been added
• The migration guide has been updated in the github wiki (What changes might users need to make in their application due to this PR?)

[sonarqubecloud]

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0 Bugs
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0 Security Hotspots
3 Code Smells

89.4% Coverage
2.7% Duplication