fp: basic katran support
Initial work to introduce katran support.
What's working:
- Add/modify/delete services
- Add/modify/delete realservers
- Traffic balancing (by client IP AND port)
- eBPF pinning
- Basic tests
- gRPC tests
What's missing:
- service flags (required to balance only by IP) [implemented in !78]
- metrics
- decide if it's OK to not include Close() as part of the ForwardingPlane interface
Bug: T380450
Edited by Vgutierrez