BUG when Trainer.test() with deepspeed stage 3

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## 🐛 Bug

Hi, I meet some bugs when I combine lightning with deepspeed follow https://pytorch-lightning.readthedocs.io/en/latest/common/trainer.html#trainer-class-api.

I find that:

- Trainer.fit() is compatible well with deepspeed stage 2 and 3 .
- Trainer.test() is compatible with deepspeed stage 2.
- There is some bugs when combine Trainer.test() with deepspeed stage 3:

> When initialize DeepSpeedStrategy with deepspeed config and then test, I will encounter this bug, I have tried to change the config, but this bug is exsited whatever.


> When initialize DeepSpeedStrategy with lightning args, I will encounter two problems, the generate speed is too slow (I used huggingface transformers and their generate() method) than the deepspeed inference scripts in https://www.deepspeed.ai/tutorials/inference-tutorial/. In addition, I also meet a bug called index of range because of self.__step of deepspeed engine.

> Hope for better compatibility between lightning and deepspeed !

cc @awaelchli @rohitgr7 @akihironitta

The issue provides no repository files or tests to inspect. Start by reproducing Trainer.test() with DeepSpeed stage 3, comparing the reported behavior with stage 2 and the DeepSpeed inference tutorial; done means the test path no longer triggers the reported error or severe generation slowdown.

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