Integrate alliander-opensource/power-grid-model as a backend

[BDonnot]

Is your feature request related to a problem? Please describe.

In order to show how to integrate a third party powerflow as a backend, it could be interesting to use https://github.com/alliander-opensource/power-grid-model as a backend.

It could also allow to test the "example/backend_integration" and make sure everything there works well.

Describe the solution you'd like

Follow the steps in the "backend_integration" (not yet merged at time of writing) and integrate the alliander-opensource/power-grid-model backend.

Describe alternatives you've considered

Additional context

If this works, powergridmodel seems also super fast. This could also be a good alternative for a fast (faster) backend in grid2op ?