eBPF based IP masquerading for external network connectivity (draft - WIP)

[vinaykul]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespaces from that line:

/kind design /kind feature /kind bug /kind cleanup /kind documentation

What this PR does / why we need it: This allows Kubernetes Pods to have external connectivity based on IP masquerading implemented in eBPF/XDP.

Which issue(s) this PR fixes:

Fixes #650

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[vinaykul]

/hold