Overhaul: Qemu Network interfaces.

[Tinyblargon]

The network adapters of ConfigQemu{} don't neatly map to the data-structure the PVE API uses.
We currently use an array.
PVE uses an map[id]settings.

With our current implementation it's not possible to have network interfaces that aren't consecutive.
In PVE users can have interface1 and interface3 configured. Our current implantation can't distinguish between.

• inteface1
• interface2

and

• interface1
• interface5

In this instance interface5 is the second interface. so it will be the second item in the array.
Before you start working on this please discuss it with me.

[Tinyblargon]

This will include #333

[Tinyblargon]

Working on this in https://github.com/Tinyblargon/proxmox-api-go/tree/%23341