Consider adding support for bridge-less networking

[networkop]

Hi 👋 , would you consider adding support for bridgeless networking using tc redirect, similar to what kata containers and fircracker-containerd are doing?
The use case is launching VMs either without any interface config or mounting/copying configuration files into the VM filesystem and activating them on boot with something like ifreload, although ultimately it'll be down to the guest image to make sure this runs.

Implementation-wise, it could a simple check that in the networking setup for loop for any configured IP addresses. If there are more than 1, then use the existing bridge+dhcp approach; if not -- setup a tc redirect between the veth and tap links.

I'd be happy to volunteer to do a PR, assuming this is deemed acceptable.

[darkowlzz]

Implemented in #836