adding advertising does a hard print

[karlp]

The callbacks for adding an advertisement are not user configurable, and simply do hard console prints: https://github.com/ukBaz/python-bluezero/blob/main/bluezero/advertisement.py#L263 and https://github.com/ukBaz/python-bluezero/blob/main/bluezero/advertisement.py#L268

If the callbacks are actually useful, we should let users handle them.

After writing this up, I realized I can probably just fix this, so I'll submit a PR for this shortly.