Update the OVN-K CNI `NetConf` struct to feature the required new attributes:

• L3 configuration
  • CIDR
  • excludeCIDRs
• optional MTU
• topology type (currently we'd have 2 values - routed / flatl2 (or overlay). 
• netAttachDefName (so you can have the same network interconnect different iface types - vfio / vf / virtio)

On top of this CNI configuration change, we need to address the CNI side of this:

• lazily add the logical switch providing the overlay representing the flat L2 network
  • accounting for the optional CIDR / excludeCIDRs
• add the corresponding LSP on this new logical switch (and configure both it and the corresponding OVS port)

Definition of done:

• PRs implementing the above merged
• e2e tests asserting these work merged