Show log messages for non-@Slot decorated listeners in more cases.

When trying to work through an issue (which resulted in https://bugreports.qt.io/browse/PYSIDE-3124) I found the 

export QT_LOGGING_RULES="qt.pyside.libpyside.warning=true" 

feature very useful. While debugging I thought of some things that could make it even more helpful (I'm not sure how feasible each of these is):

• Report Slot decorated methods or functions that are not members of a QObject based class.
• Report QObject classes that neglect to run super()._init_()
  • Ensure that Non-slot listeners are reported on QObject based classes even when super()._init_() is not called.
• Report non-slot Signal listeners in general (could work as mostly a catch all for the above cases).

Ideally the included example would emit 5 more warning than it currently does. 3 for the connecting non-slot/incorrectly setup listeners. 1 for failing to call super()._init() in the classes __init_() method. 1 for Slot decorating a non-Qbject method.

Even just a subset of these would be useful.