Support PQ to ReactivePower switching in the reactive limit outer loop

[Hadrien-Godard]

Describe the current behavior

If a bus controls reactive power and is switched to PQ bus in the reactive limit outer loop, then it is never to switch it back to reactive power control.

Describe the expected behavior

If a bus controls reactive power and is switched to PQ bus in the reactive limit outer loop, then it is possible that it is switched back to reactive power control if conditions have improved.

Describe the motivation

The motivation is to better model the fact that different controls can positively interact so all targets are valid.

Extra Information

In ReactiveLimitsOuterLoop class, there is a need to update "private static void checkPqBus". Indeed this function should be able to implement a PQ -> PV switch but also a PQ -> Reactive Control switch.

The exact criterion is to be designed but can use a sensitivity from control bus Q to controlled terminal Q.