SimG4CrossingAngleBoost should be moved to k4Gen

[gganis]

It is a generator related tool.

[EmanuelPerez]

I think that we better generate "raw" gen-level events: no crossing angle, no vertex smearing. And introduce them in the SIM step. Then, the same gen-level events can be used to produce simulated events corresponding to a different vertex smearing (which is related to the beam parameters, which themselves are a moving target); or to simulate events with/without the crossing angle, if we wanted to study the effect. Only the case of BES is different, since that DOES impact the generation step, in contrast to the angle (transverse boost) of the vertex smearing (global shift of the origin).

Having the angle in the gen-level step only matters for very, very specialised purpose (programs that do generate beam-beam effects like Guinea-Pig, and these programs do implement the crossing angle already).