Debugger should register the Python `dbg` object

[xusheng6]

As in https://github.com/Vector35/binaryninja-api/blob/15c635b873105eda2861430d062ea3f6bdfe9d9b/python/scriptingprovider.py#L1532-L1535

[xusheng6]

It should be done in the same way as https://github.com/Vector35/binaryninja-api/blob/768f7c78465fb93936e5ca50a0ca712664fe54e7/view/kernelcache/api/python/kernelcache.py#L193-L210