Make use of bond optionnal

In !42 (merged) we changed the behavior of libvirt-metal pods to expose a bonded configuration to the virtual machine.

However, we observed in sylva-projects/sylva-core#1581 (closed) that it was breaking upgrade from 1.1.1 to main pipelines, and had to disable it by downgrading the version of libvirt-metal used in these pipelines in sylva-projects/sylva-elements/ci-tooling/ci-deployment-values!64 (merged).

Anyway, if we need to leverage new features of libvirt-metal in main before we release 1.2.0 (like enableDHCP option for DHCP-less testing for example), we'll have to add an option to re-expose plain interfaces as before in order to be able to use a newer version of libvirt-metal for main in these pipelines.