Fix detection of predictable network interface names

E.g. virtio drivers might have the properties ID_NET_NAME_PATH=enp0s18
and ID_NET_NAME_SLOT=ens18. If we check only for ID_NET_NAME_PATH, then
we end up with a network configuration for enp0s18, while the actual
network interface name will be ens18.

So instead look at all present network devices, iterate over them
(ignoring the virtual interfaces like bridges + vboxnet) and
check for present ID_NET_NAME_* settings, using the following precedence
(as defined in link_config_apply() of systemd/src/udev/net/link-config.c):

* ID_NET_NAME_FROM_DATABASE
* ID_NET_NAME_ONBOARD
* ID_NET_NAME_SLOT
* ID_NET_NAME_PATH
* ID_NET_NAME_MAC

Closes: #929810