Optimizer load gathered state and record delta feature are supported now

[MayDomine]

AdamOffloadOptimizer new feature

Description

为AdamOffload提供两个新的新接口

1. 位于AdamOffloadOptimizer的__init__(self)里传递record_delta=True，将记录adam每个step更新量的统计信息。

2. AdamOffloadOptimizer的state_dict(self)里传递gather=True，将对所有rank的opt进行gather得到完整的grad ckpt（注意该功能在大模型上可能会使cpu内存炸掉），并且该完整ckpt可以使用optimizer.load_state_dict(torch.load(filename))直接加载（无论在单卡还是多卡），即多卡可以同时加载一个完整的grad ckpt，因为在写文件时会添加一个标识意味着该文件为完整ckpt，从而load每个rank内再切出属于自己的那一份grad

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

Additional Information

Any additional information, configuration, or data that might be necessary for the review.