This builds a bundle with CNI plugins for talosctl which is
automatically downloaded by `talosctl` if CNI plugins are missing.
CNI directories are moved by default to the `~/.talos/cni` path.
Also add a bunch of pre-flight checks to the QEMU provisioner to make it
easier to bootstrap the Talos QEMU cluster.
Signed-off-by: Andrey Smirnov <smirnov.andrey@gmail.com>