Embedded Network Manager API for Qt

Boot to Qt today has a network settings feature from the old device utilities code base. Since it has a number of identified deficiencies the intent is to replace that with a new network manage and get rid of all the older device utilities code. This ticket covers an API to access existing QNetwork module to build the new network manager similar to what desktop linux distributions have today. The concept is the same as in device utilities today, the new network API should allow similar functionality:
https://doc.qt.io/QtDeviceUtilities/qtnetworksettings-module.html

The embedded requirements for the new network manager API are:

-support wifi and fixed ethernet including at least:
----network discovery
----initialising network connection
----shutting down network connection
----ability to get the IP address of the embedded board where the network manager is running. This is needed for Creator setup.
----support both IPv4 and IPv6 addresses
----support proxy configuration
----network interface state and type
----network interface authentication with user credentials

-support a number of different backends in a cross-platform fashion, as opposed to boot to qt using only connman today: Supporting Windows and Linux at least in the target hardware.
-The C++ API should be part of existing Qt Network module

Having ready made UI elements for network management in e.g. Qt Quick can be treated as a separate activity outside of this ticket.

The other features from Qt5 device utilities have been removed already in Qt6 side so we do not have to worry about them here.