wifi: Fix access point updates for the active connection

This fixes the active connection always getting the parameters of the reference access point (the strongest signal), instead of the active AP (the one we're currently connected to), which is typical on automatic dual band wireless networks (2,4/5GHz).

A new slot is created to update the item when the active AP actually changes.

The following examples show the Details info provided by the model item v. the information from nmcli device wifi. Currently, we are updating the netowrk parameters, such as signal strenght, from the first item (the reference AP) instead of the one in use (the active AP).

BEFORE	referenceAP-info-before
AFTER	referenceAP-info-after