Implement traffic command

[yokaze]

This PR implements npv traffic command.

Usage

• npv traffic -n [NAMESPACE]
• npv traffic -n [NAMESPACE] [POD]
• npv traffic -n [NAMESPACE] -l [SELECTOR]

When multiple pods are selected, it shows the combined traffic amount.

Example Result

$ npv traffic -n test -l test=self
DIRECTION IDENTITY NAMESPACE EXAMPLE                                        PROTOCOL PORT BYTES PACKETS
Egress    2        -         cidr:1.1.1.1/32                                UDP      53   558   6
Egress    2        -         cidr:8.8.8.8/32                                UDP      53   558   6
Egress    22197    test      l4-ingress-explicit-allow-tcp-674bf84548-vbk7k TCP      8000 5820  72
Egress    23557    test      l3-ingress-explicit-allow-all-854c9bb96c-96nqs ANY      ANY  5808  72

Implementation

1. npv traffic computes the list of pods, for which the traffic amount should be displayed
2. It asks cilium-agent on each node through cilium-agent-proxy to query BPF policy map, along with traffic amount for each route (similar to npv inspect)
3. It selects allowed and active (traffic > 0) routes
4. Combine the traffic amount for pods and display the result

CI update

Overview: e2e/testdata/policy/README.md

This PR:

• raises self pod from one to two, to check npv traffic shows combined traffic amount
• changes test pods from ubuntu to testhttpd, to make real traffic
• allows self pods to reach 1.1.1.1 (Cloudflare DNS)