Handling custom exception type from activities

I would like to understand if it is possible to handle custom exception type (from activities) inside the orchestrator function.

E.g.:

Activity
```python
raise MyException(custom_data={...})
```
Orchestrator:
```python
try:
res = yield context.call_activity("Activity", data)
except MyException as me:
print(me.custom_data)
```

The actual behaviour is that in the orchestrator function I only get the generic Exception type and I cannot differentiate the handle logic based on custom_data.

首先复现引发 MyException 的 Activity 以及调用 context.call_activity 的 orchestrator，然后跟踪 Activity 异常如何到达 orchestrator。完成标准是确定是否可以保留自定义异常类型和 custom_data，以便进行差异化处理，并记录或实现所需行为。

由索引模型根据 Issue 内容生成。