bgpv1-cp: introduce nodespecer interface
bgpv1-cp: introduce nodespecer interface

the BGP control plane needs to access the hosting Node's PodCIDR ranges.
the way these ranges are accessed can change dependent on the IPAM mode
Cilium is configured with.

in order to provide a singular API to the control plane, introduce an
interface which abstracts the differences between obtaining NodeSpec
information from a Kubernetes Node and a CiliumNode resource.

Signed-off-by: Louis DeLosSantos <e7ae6d6e1769b56e461abca13c275680721e78d7@isovalent.com>

michi-covalent/cilium,michi-covalent/cilium,michi-covalent/cilium,cilium/cilium,michi-covalent/cilium,cilium/cilium,cilium/cilium,michi-covalent/cilium,cilium/cilium,cilium/cilium