message: WIP: update the test
  note: when disable mixed precision, some of them can not reach double criterion
diff: @@ -266,6 +266,7 @@ protected:
  using CoarseNext = gko::multigrid::Pgm<gko::next_precision<value_type>>;
  using Smoother = gko::preconditioner::Jacobi<value_type>;
  using CoarsestSolver = gko::solver::Cg<value_type>;
  + using CoarsestNextSolver = gko::solver::Cg<gko::next_precision<value_type>>;
  using DummyRPFactory = DummyMultigridLevelWithFactory<value_type>;
  using DummyFactory = DummyLinOpWithFactory<value_type>;
  Multigrid()
  @@ -301,6 +302,14 @@ protected:
  .with_reduction_factor(r<value_type>::value)
  .on(exec))
  .on(exec)),
  + coarsestnext_factory(
  + CoarsestNextSolver::build()
  + .with_criteria(
  + gko::stop::Iteration::build().with_max_iters(4u).on(exec),
  + gko::stop::Time::build()
  + .with_time_limit(std::chrono::seconds(6))
  + .on(exec))
  + .on(exec)),
  rp_factory(DummyRPFactory::build().on(exec)),
  lo_factory(DummyFactory::build().on(exec)),
  b(gko::initialize<Mtx>({I<value_type>({1, 0}), I<value_type>({0, 2}),
  @@ -374,13 +383,13 @@ protected:
  Solver::build()
  .with_pre_smoother(smoother_factory)
  .with_smoother_relax(1.0)
  - .with_coarsest_solver(coarsest_factory)
  + .with_coarsest_solver(coarsestnext_factory)
  .with_max_levels(2u)
  .with_post_uses_pre(true)
  .with_mid_case(gko::solver::multigrid::mid_smooth_type::both)
  .with_mg_level(coarse_factory, coarsenext_factory)
  .with_criteria(
  - gko::stop::Iteration::build().with_max_iters(100u).on(exec),
  + gko::stop::Iteration::build().with_max_iters(200u).on(exec),
  gko::stop::Time::build()
  .with_time_limit(std::chrono::seconds(100))
  .on(exec),
  @@ -469,6 +478,7 @@ protected:
  std::shared_ptr<typename CoarseNext::Factory> coarsenext_factory;
  std::shared_ptr<typename Smoother::Factory> smoother_factory;
  std::shared_ptr<typename CoarsestSolver::Factory> coarsest_factory;
  + std::shared_ptr<typename CoarsestNextSolver::Factory> coarsestnext_factory;
  std::shared_ptr<typename DummyRPFactory::Factory> rp_factory;
  std::shared_ptr<typename DummyFactory::Factory> lo_factory;
  std::shared_ptr<Mtx> b;
  