This reverts commit 9beb154b.

This reverts commit c641fb3c.

This reverts commit a41a5bcb.

This reverts commit afc9b4c6.

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

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.

https://github.com/PaddlePaddle/PaddleClas/pull/2633