This reverts commit ab29eaa8.

This reverts commit a41a5bcb.

This reverts commit 9e683d0d.

This reverts commit afc9b4c6.

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.