[Refine] Remove redundant code

[HydrogenSulfate]

PR types

Function optimization

PR changes

Others

Describe

1. 删除随机种子固定、logger初始化代码，在yaml中通过callback控制，如下所示

   # set random seed for reproducibility
   ppsci.utils.misc.set_random_seed(cfg.seed)
   # initialize logger
   logger.init_logger("ppsci", osp.join(cfg.output_dir, "train.log"), "info")

2. 当drop_last和shuffle均为False时，可以省略sampler配置字段，删除如下冗余代码

   "sampler": {
       "name": "BatchSampler",
       "drop_last": False,
       "shuffle": False,
   },

3. num_workers默认为1，因此删除手动指定的代码。

4. 配置文件添加默认值SolverConfig，化简config模块相关代码，当指定了cfg参数时，不需要传入除model、constraint、equation、validator等必要参数之外的其他超参数，否则保持原状，兼容已有代码。

   # before solver = ppsci.solver.Solver( model, constraint, cfg.output_dir, optimizer, lr_scheduler, cfg.TRAIN.epochs, cfg.TRAIN.iters_per_epoch, save_freq=cfg.TRAIN.save_freq, log_freq=cfg.log_freq, eval_during_train=True, eval_freq=cfg.TRAIN.eval_freq, seed=cfg.seed, equation=equation, geom=geom, validator=validator, visualizer=visualizer, pretrained_model_path=cfg.TRAIN.pretrained_model_path, checkpoint_path=cfg.TRAIN.checkpoint_path, eval_with_no_grad=cfg.EVAL.eval_with_no_grad, )

   # after solver = ppsci.solver.Solver( model, constraint, optimizer=optimizer, equation=equation, validator=validator, visualizer=visualizer, cfg=cfg, )

TODO: 文档代码块位置更新

[paddle-bot]

Thanks for your contribution!