Improve static safety of repo by using generic types and custom constructors

As per our discussion here: https://github.com/Azure/azure-functions-durable-python/pull/184#pullrequestreview-544266683

Data such as the Entity batch array would be safer to use if registered as their own datatype. This way, we can prevent invalid operations across the codebase.

We should do a scan of the codebase and improve all the cases where custom types could be used to prevent invalid operation.

从 pull request 184 中的讨论开始，尤其是查看关联的 review，并检查 Entity batch array example。然后扫描代码库，查找其他可能通过自定义类型或构造函数来阻止无效操作的地方。当相关数据结构在整个代码库中一致地使用更安全的类型时，即视为完成。

由索引模型根据 Issue 内容生成。