Inconsistent naming get_json() in EventGridEvent and EventGridOutputEvent

Both mentioned classes have methods called `get_json` which return the classes `__data` field. This seems odd for two reasons:

1. They don't actually return JSON but a dict (if the typing hints in `__init__` are correct). In any case this is a major source of confusion.
2. All other getters are implemented as properties. (So why not just do the same here?)

https://github.com/Azure/azure-functions-python-library/blob/44712a77ce6ba68065d1c16ed6015bb998ddfe48/azure/functions/_eventgrid.py#L33-L34

https://github.com/Azure/azure-functions-python-library/blob/44712a77ce6ba68065d1c16ed6015bb998ddfe48/azure/functions/_eventgrid.py#L86-L87

从 azure/functions/_eventgrid.py 的第 33-34 行和第 86-87 行开始，然后将这些访问器与 EventGridEvent 和 EventGridOutputEvent 上的其他 getter 进行比较。统一解决命名和 property 行为，同时确认最终的 API 能够反映该值是 dict 而不是 JSON。

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