Python3: fix NVDA's logging infrastructure (#9712)
* The logging._levelNames dict no longer exists in Python 3. Instead, we now use logging.getLevelName.
* logHandler: We can now use logging.FileHandler rather than logging.StreamHandler and assume unicode all the way until writing the file to disk with utf8.
logHandler: FunctionType.func_code is now FunctionType.__code__.
# Please enter the commit message for your changes. Lines starting
* logHandler: address review comments.
