connectivity: Introduce BGP CP connectivity tests

[rastislavs]

Introduces BGP Control Plane connectivity tests, working with FRR router instance running in the host network namespace on the node-without-cilium.

The aim of this PR is mostly to introduce the BGP + FRR testing infrastructure, more testing scenarios need to be added in follow-up PRs. At the moment, we are testing:

• BGPv1 control plane, IPv4 + IPv6 scenario,
• BGPv2 control plane, IPv4 + IPv6 scenario,
• in both scenarios we test PodCIDR advertisements and ClusterIP service advertisements.

Example run with debug enabled:

[=] [cilium-test] Test [bgp-control-plane-v1] [80/84]
  [.] Action [bgp-control-plane-v1/bgpv1-advertisements/curl-echo-pod-ipv4-0: cilium-test/echo-external-node-89864b5bd-4lzt4 (172.22.0.4) -> cilium-test/echo-same-node-7f896b84-sbqv4 (10.244.1.188:8080)]
  🐛 Executing command [curl -w %{local_ip}:%{local_port} -> %{remote_ip}:%{remote_port} = %{response_code} --silent --fail --show-error --output /dev/null --connect-timeout 2 --max-time 10 http://10.244.1.188:8080]
.  [.] Action [bgp-control-plane-v1/bgpv1-advertisements/curl-echo-pod-ipv4-1: cilium-test/echo-external-node-89864b5bd-4lzt4 (172.22.0.4) -> cilium-test/echo-other-node-58999bbffd-qsrq8 (10.244.0.254:8080)]
  🐛 Executing command [curl -w %{local_ip}:%{local_port} -> %{remote_ip}:%{remote_port} = %{response_code} --silent --fail --show-error --output /dev/null --connect-timeout 2 --max-time 10 http://10.244.0.254:8080]
  [.] Action [bgp-control-plane-v1/bgpv1-advertisements/curl-echo-service-ipv4-0: cilium-test/echo-external-node-89864b5bd-4lzt4 (172.22.0.4) -> cilium-test/echo-same-node (10.96.136.144:8080)]
  🐛 Executing command [curl -w %{local_ip}:%{local_port} -> %{remote_ip}:%{remote_port} = %{response_code} --silent --fail --show-error --output /dev/null --connect-timeout 2 --max-time 10 http://10.96.136.144:8080]
..  [.] Action [bgp-control-plane-v1/bgpv1-advertisements/curl-echo-service-ipv4-1: cilium-test/echo-external-node-89864b5bd-4lzt4 (172.22.0.4) -> cilium-test/echo-other-node (10.96.194.250:8080)]
  🐛 Executing command [curl -w %{local_ip}:%{local_port} -> %{remote_ip}:%{remote_port} = %{response_code} --silent --fail --show-error --output /dev/null --connect-timeout 2 --max-time 10 http://10.96.194.250:8080]
.  [.] Action [bgp-control-plane-v1/bgpv1-advertisements/curl-echo-pod-ipv6-0: cilium-test/echo-external-node-89864b5bd-4lzt4 (fc00:c111::4) -> cilium-test/echo-other-node-58999bbffd-qsrq8 (fd00:10:244::9227:8080)]
  🐛 Executing command [curl -w %{local_ip}:%{local_port} -> %{remote_ip}:%{remote_port} = %{response_code} --silent --fail --show-error --output /dev/null --connect-timeout 2 --max-time 10 http://[fd00:10:244::9227]:8080]
.  [.] Action [bgp-control-plane-v1/bgpv1-advertisements/curl-echo-pod-ipv6-1: cilium-test/echo-external-node-89864b5bd-4lzt4 (fc00:c111::4) -> cilium-test/echo-same-node-7f896b84-sbqv4 (fd00:10:244:1::1a8:8080)]
  🐛 Executing command [curl -w %{local_ip}:%{local_port} -> %{remote_ip}:%{remote_port} = %{response_code} --silent --fail --show-error --output /dev/null --connect-timeout 2 --max-time 10 http://[fd00:10:244:1::1a8]:8080]
  [.] Action [bgp-control-plane-v1/bgpv1-advertisements/curl-echo-service-ipv6-0: cilium-test/echo-external-node-89864b5bd-4lzt4 (fc00:c111::4) -> cilium-test/echo-same-node (fd00:10:96::4567:8080)]
  🐛 Executing command [curl -w %{local_ip}:%{local_port} -> %{remote_ip}:%{remote_port} = %{response_code} --silent --fail --show-error --output /dev/null --connect-timeout 2 --max-time 10 http://[fd00:10:96::4567]:8080]
..  [.] Action [bgp-control-plane-v1/bgpv1-advertisements/curl-echo-service-ipv6-1: cilium-test/echo-external-node-89864b5bd-4lzt4 (fc00:c111::4) -> cilium-test/echo-other-node (fd00:10:96::4763:8080)]
  🐛 Executing command [curl -w %{local_ip}:%{local_port} -> %{remote_ip}:%{remote_port} = %{response_code} --silent --fail --show-error --output /dev/null --connect-timeout 2 --max-time 10 http://[fd00:10:96::4763]:8080]
.  🐛 Finalizing Test bgp-control-plane-v1
  [-] Scenario [bgp-control-plane-v2/bgpv2-advertisements]
[=] [cilium-test] Test [bgp-control-plane-v2] [81/84]
  [.] Action [bgp-control-plane-v2/bgpv2-advertisements/curl-echo-pod-ipv4-0: cilium-test/echo-external-node-89864b5bd-4lzt4 (172.22.0.4) -> cilium-test/echo-other-node-58999bbffd-qsrq8 (10.244.0.254:8080)]
  🐛 Executing command [curl -w %{local_ip}:%{local_port} -> %{remote_ip}:%{remote_port} = %{response_code} --silent --fail --show-error --output /dev/null --connect-timeout 2 --max-time 10 http://10.244.0.254:8080]
.  [.] Action [bgp-control-plane-v2/bgpv2-advertisements/curl-echo-pod-ipv4-1: cilium-test/echo-external-node-89864b5bd-4lzt4 (172.22.0.4) -> cilium-test/echo-same-node-7f896b84-sbqv4 (10.244.1.188:8080)]
  🐛 Executing command [curl -w %{local_ip}:%{local_port} -> %{remote_ip}:%{remote_port} = %{response_code} --silent --fail --show-error --output /dev/null --connect-timeout 2 --max-time 10 http://10.244.1.188:8080]
.  [.] Action [bgp-control-plane-v2/bgpv2-advertisements/curl-echo-service-ipv4-0: cilium-test/echo-external-node-89864b5bd-4lzt4 (172.22.0.4) -> cilium-test/echo-other-node (10.96.194.250:8080)]
  🐛 Executing command [curl -w %{local_ip}:%{local_port} -> %{remote_ip}:%{remote_port} = %{response_code} --silent --fail --show-error --output /dev/null --connect-timeout 2 --max-time 10 http://10.96.194.250:8080]
.  [.] Action [bgp-control-plane-v2/bgpv2-advertisements/curl-echo-service-ipv4-1: cilium-test/echo-external-node-89864b5bd-4lzt4 (172.22.0.4) -> cilium-test/echo-same-node (10.96.136.144:8080)]
  🐛 Executing command [curl -w %{local_ip}:%{local_port} -> %{remote_ip}:%{remote_port} = %{response_code} --silent --fail --show-error --output /dev/null --connect-timeout 2 --max-time 10 http://10.96.136.144:8080]
.  [.] Action [bgp-control-plane-v2/bgpv2-advertisements/curl-echo-pod-ipv6-0: cilium-test/echo-external-node-89864b5bd-4lzt4 (fc00:c111::4) -> cilium-test/echo-other-node-58999bbffd-qsrq8 (fd00:10:244::9227:8080)]
  🐛 Executing command [curl -w %{local_ip}:%{local_port} -> %{remote_ip}:%{remote_port} = %{response_code} --silent --fail --show-error --output /dev/null --connect-timeout 2 --max-time 10 http://[fd00:10:244::9227]:8080]
.  [.] Action [bgp-control-plane-v2/bgpv2-advertisements/curl-echo-pod-ipv6-1: cilium-test/echo-external-node-89864b5bd-4lzt4 (fc00:c111::4) -> cilium-test/echo-same-node-7f896b84-sbqv4 (fd00:10:244:1::1a8:8080)]
  🐛 Executing command [curl -w %{local_ip}:%{local_port} -> %{remote_ip}:%{remote_port} = %{response_code} --silent --fail --show-error --output /dev/null --connect-timeout 2 --max-time 10 http://[fd00:10:244:1::1a8]:8080]
.  [.] Action [bgp-control-plane-v2/bgpv2-advertisements/curl-echo-service-ipv6-0: cilium-test/echo-external-node-89864b5bd-4lzt4 (fc00:c111::4) -> cilium-test/echo-same-node (fd00:10:96::4567:8080)]
  🐛 Executing command [curl -w %{local_ip}:%{local_port} -> %{remote_ip}:%{remote_port} = %{response_code} --silent --fail --show-error --output /dev/null --connect-timeout 2 --max-time 10 http://[fd00:10:96::4567]:8080]
.  [.] Action [bgp-control-plane-v2/bgpv2-advertisements/curl-echo-service-ipv6-1: cilium-test/echo-external-node-89864b5bd-4lzt4 (fc00:c111::4) -> cilium-test/echo-other-node (fd00:10:96::4763:8080)]
  🐛 Executing command [curl -w %{local_ip}:%{local_port} -> %{remote_ip}:%{remote_port} = %{response_code} --silent --fail --show-error --output /dev/null --connect-timeout 2 --max-time 10 http://[fd00:10:96::4763]:8080]
.  🐛 Finalizing Test bgp-control-plane-v2

Example e2e job: https://github.com/cilium/cilium/actions/runs/9778585998/job/26995747615