Support `lima:shared`, `lima:bridged`, `lima:host` on Linux hosts

[AkihiroSuda]

At KubeCon @nirs suggested me to adopt libvirtd's standard to managing networks.

https://wiki.libvirt.org/VirtualNetworking.html

Our implementation may invoke the same brctl commands used by libvirtd, however, it should not introduce a dependency on libvirtd

[nirs]

If we don't depend on libvirt, we need to reinvent part of it. We will need a daemon running as root that can set up the network for qemu. My suggestion was to use libvirt API on Linux. This is how minikube kvm driver is implemented, and we are a happy user of minikube on Linux :-)

We can use a pluggable driver depending on libvirt. It will require modifying lima to separate the networking code from the main program.