typing: connect() and disconnect() do not accept SIGNAL() and SLOT() values

SIGNAL() and SLOT() are declared as returning strings. However, many methods who are expecting arguments as result from SIGNAL and SLOT accept only byte-like input.

This applies to :

• QObject.connect
• QObject.disconnect
• QObject.receivers
• SignalInstance.connect
• SignalInstance.disconnect

I have an example code to check this but it's quite long as it checks all possibilities and return values.

This fix rather simple, all above methods should accept string instead of byte-like object