Avoid getBestSolution() cast by generifying Solver and SolverFactory and return the best solution from solve()

        SolverFactory solverFactory = SolverFactory.createFromXmlResource(
                "org/optaplanner/examples/cloudbalancing/solver/cloudBalancingSolverConfig.xml");
        Solver solver = solverFactory.buildSolver();
        CloudBalance unsolvedCloudBalance = ...;
        
        solver.solve(unsolvedCloudBalance);
        CloudBalance solvedCloudBalance = (CloudBalance) solver.getBestSolution();

        SolverFactory<CloudBalance> solverFactory = SolverFactory.createFromXmlResource(
                "org/optaplanner/examples/cloudbalancing/solver/cloudBalancingSolverConfig.xml");
        Solver<CloudBalance> solver = solverFactory.buildSolver();
        CloudBalance unsolvedCloudBalance = ...;

        solver.solve(unsolvedCloudBalance);
        CloudBalance solvedCloudBalance = solver.getBestSolution();

        SolverFactory<CloudBalance> solverFactory = SolverFactory.createFromXmlResource(
                "org/optaplanner/examples/cloudbalancing/solver/cloudBalancingSolverConfig.xml");
        Solver<CloudBalance> solver = solverFactory.buildSolver();
        CloudBalance unsolvedCloudBalance = ...;
        
        CloudBalance solvedCloudBalance = solver.solve(unsolvedCloudBalance);