Dicts with non-string keys get serialized wrong

Copied from with more discussion at: https://github.com/qiemem/PythonExtension/issues/6

Some examples:

observershow py:runresult "{1: 2}"
observer: [["1" 2]]
observershow py:runresult "{(1,2): 3}"
Extension exception: keys must be a string

While JSON is restricted to string keys, we are not. We need to hijack JSON's dict serialization to turn them into a list of pairs instead.

首先跟踪 Python extension 如何处理 py:runresult 示例，以及字典在哪里经过 JSON 序列化传递。复现 {1: 2} 和 {(1,2): 3} 这两种情况，然后验证非字符串键字典是否会序列化为成对元素的列表，而不会产生当前不正确的输出或异常。