[Feature] Cilium BGP Control Plane

**Is your feature request related to a problem? Please describe.**
Cilium BGP support allows AKS clusters to participate in BGP routing and allows exposing pods and services. This can simplify architectures and reduce the need for additional LBs.

https://docs.cilium.io/en/latest/network/bgp-control-plane/bgp-control-plane/

**Describe the solution you'd like**
Azure CNI Powered by Cilium should support BGP as well as upstream CRDs.

**Describe alternatives you've considered**
N/A

**Additional context**
N/A