Merge: model: Add `mpackage` importation hierarchy

Merge: model: Add `mpackage` importation hierarchy

Added a `mpackage_importation_hierarchy` graph to keep the hierarchy of packages. The packages relations are defined when the `set_imported_mmodules` is called.

This pr is related to the programming by contract. The objective is to determine when the use of a contract is necessary in a given context.

Note in this graph all the packages are in relation with themself.

example for all nitc package hierarchy :

![](https://sendeyo.com/up/d/514e168e33)

This pr has a dependency with the #2784

Pull-Request: #2788
Reviewed-by: Jean Privat <jean@pryen.org>
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>