[auto-parallel] add auto-offload feature (#3154)

* add auto-offload feature

* polish code

* fix syn offload runtime pass bug

* add offload example

* fix offload testing bug

* fix example testing bug

examples/language/gpt/experiments/auto_offload/README.md

@@ -0,0 +1,37 @@
+# Auto-Offload Demo with GPT2
+
+## Requirements
+
+Before you can launch training, you need to install the following requirements.
+
+### Install PyTorch
+
+```bash
+#conda
+conda install pytorch==1.12.0 torchvision==0.13.0 torchaudio==0.12.0 cudatoolkit=11.3 -c pytorch
+#pip
+pip install torch==1.12.0+cu113 torchvision==0.13.0+cu113 torchaudio==0.12.0 --extra-index-url https://download.pytorch.org/whl/cu113
+```
+
+### Install [Colossal-AI v0.2.0](https://colossalai.org/download/) From Official Website
+
+```bash
+pip install colossalai==0.2.0+torch1.12cu11.3 -f https://release.colossalai.org
+```
+
+### Install transformers
+
+```bash
+pip install transformers
+```
+
+## Dataset
+
+For simplicity, the input data is randonly generated here.
+
+## Training
+
+```bash
+#Run the auto offload on GPT with default setting and a dummy dataset.
+bash run.sh
+```