This reverts commit 9beb154b.

This reverts commit 392b75b1.

This reverts commit c30df630.

This reverts commit 58daf805.

This reverts commit 428edb6f.

This reverts commit 106ff270.

This reverts commit 9e683d0d.

This reverts commit ac27cb19.

This reverts commit 2a61ac65.

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.