Add additionnal test for pypowsybl backend

[RalfCortes]

Hello,

As shown here : powsybl/pypowsybl#1182 there seems to be a bug in the pypowsybl backend implementation regarding load Q updates.
This was not found until recently, so we could add some safety checks in grid2op for the future.

[BDonnot]

Will be done in version 1.12.4

[BDonnot]

Done and merged :-)

There were no issue to this regards fortunately.