[Feature] Support customized model size for training

### 描述该功能

hi there,

could you give some suggestions for training small model size, such as 1B or 3B, and related configurations?

thanks a ton!

### 是否希望自己实现该功能？

- [ ] 我希望自己来实现这一功能，并向 InternLM 贡献代码！