[FEA] VRP/PDP without vehicle minimization

In some vehicle routing scenarios the primary goal is to minimize the total supply time. Users of such solvers fairly assume the amount of vehicles is enough to deliver the orders.

Therefore, a mode in cuOpt that focuses primarily on minimizing the total travel time or cost, is required.

It is currently possible to use cuOpt as a solver which minimizes total cost/travel_time without minimizing the vehicles count. The approach is to assign each order to a placeholder vehicle, and each placeholder vehicle to a dummy order with 0 travel time. Clearly this will enforce the solver to use N_vehicles = N_orders, and if the only order assigned to a vehicle is fake, it means that vehicle is not used in the solution.

But this formulation doubles the problem size. Moreover, Guided Ejection Search is still observed in call stack though that doesn't do anything useful.

If there's something I have missed in the documentation, I'd be very grateful to get help with this. Otherwise, I would like to discuss how to disable vehicle minimization in cuOpt efficiently.