IFinterpolator: Core-collapse of secondary star

The IF interpolator for core-collapse (CC) quantities is only trained for the collapse of the primary.

While it's rare that the secondary will explode first, we do not train any IF interpolators for such situations. These binaries might fail or do the collapse calculation using core masses or the NN. (which might mean properties will be missing).

Furthermore, we should investigate that these rare events are correctly considered in the final S1/S2_state classifier and the IF interpolator values. No clear direction for this, but an important check if one wants to talk about mass ratio reversal in the HMS-HMS grid or more unique formation channels.