This reverts commit 187f38eb.

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This reverts commit 32593b63.

This reverts commit d3374e89.

This reverts commit 9beb154b.

This reverts commit 392b75b1.

This reverts commit c30df630.

This reverts commit 58daf805.

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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.