This reverts commit d3941dc1.

This reverts commit 32593b63.

This reverts commit d3374e89.

This reverts commit 9beb154b.

This reverts commit 392b75b1.

This reverts commit c30df630.

This reverts commit 106ff270.

This reverts commit ac27cb19.

1. rm Global.eval_mode
2. add Global.task
3. mv type_name to ppcls.utils
4. build dataloader, loss, metric by mode

1. ModelSaver();
2. _build_ema_model();
3. _init_checkpoints();
4. others.

1. rm engine.device and use paddle.device.get_device() instead;
2. mv some code to build_train_func or build_eval_func to simpfy engine.