Rework -netdev parameters syntax and get the current patch in shape for upstream qemu.
This qemu patchset by Laurent Vivier should soon land upstream: https://patchew.org/QEMU/20221021090922.170074-1-lvivier@redhat.com/ once it's there, I'll take care of adjustments and documentation updates in passt.
Merged in qemu as commit 13c6be96618c, available since version 7.2.