RTE use case - plot grid state after line disconnection in Anticipation cards

[marota]

The contextual network view should reflect the grid state after the N-1 line disconnection of an anticipation card, not before that.

Currently the same forecasted grid state is displayed for every anticipation cards which is confusing for users as there are looking for which line got disconnected and where are the resulting overloads (which they don't see currently)

[marota]

We should get one obs_forecast per N-1 anticipation card:
https://github.com/IRT-SystemX/InteractiveAI/blob/706f0b9254420a50e77b714e1cdd59ee3851d1fa/usecases_examples/rte/app/models/Simulator.py#L226C17-L228C86

such that
# pour dans 15 min (time_step_forecast=3)
obs_forecast_n_1, *_ = self.obs.simulate(self.env.action_space({set_line_status:[(N_1_line_name,-1)]}),

And then generate individual images here for each N-1, not one image for all:

InteractiveAI/usecases_examples/rte/app/models/Simulator.py

Line 393 in 706f0b9

if not img_b64_forecast: