[th/udev-auto-link-local-only] honor ID_NET_AUTO_LINK_LOCAL_ONLY udev property
We honored "NM_AUTO_DEFAULT_LINK_LOCAL_ONLY" udev property, for when we
generate a "Wired connection 1" (aka the "auto-default connection").
Systemd now also honors and may set ID_NET_AUTO_LINK_LOCAL_ONLY for
a similar purpose. Honore that too.
The NM specific variable still is preferred, also because "NM_AUTO_DEFAULT_LINK_LOCAL_ONLY"
is about something very NetworkManager specific (controlling "Wired connection 1").
Maybe one day, we should drop "data/90-nm-thunderbolt.rules" and only rely on what systemd provides. But not yet.
Also adds support for ID_NET_MANAGED_BY=. See