Support different cloud-init network-config

[mcbenjemaa]

Describe the solution you'd like

Currently we only support network-config version 2 which supports netplan distributions.

We need a way of making this configurable so the user can choose which network-config version to use.

Anything else you would like to add:

This will make sure capmox supports various distributions

[65278]

This is a can of worms, we support features which are not supported by cloudinit network-config version 1, so we can't just naively convert with a different template. In fact, we only support netplan passthrough.
If we decide to support this, at the very least we need to document features which will not work.

[65278]

Some thoughts: since this is a "per proxmox template" issue, we can't make this a controller environment variable. The information of what renderer to use would need to live in the proxmox machine templates themselves (as they reference templateID).
An optional variable here could allow us to call a different renderer.