Generic bearer plugin cannot detect BearerType on Windows anymore

Currently the generic bearer plugin cannot detect the bearer type on Windows.

This is most likely a regression from https://codereview.qt-project.org/#/c/123237 since the network interface name changed. This name was used in
static QNetworkConfiguration::BearerType qGetInterfaceType(const QString &interface)
to open it as IO device. Since the name change, the method always returns BearerUnknown. This causes very annoying effects since ethernet and wifi adapters do not get priority anymore in QNetworkConfigurationManager::defaultConfiguration(). If multiple interfaces are connected, a random interface, in my case a teredo tunnel adapter which happened to be connected for some reason was returned instead of the active ethernet connection. The end result was that at some point, network accessible changed to not accessible and all network access was blocked.

Reverting the above change fixes it, but I let the assignee decide how to handle it and keep the nice names.