feat: implement checksum

[jokestax]

Description

• Use bpf_l3_csum_replace and bpf_l4_csum_replace instead of bpf_csum_diff.
• Implement checksum updates for both IP and TCP headers after modifying source IP/port.

[k8s-ci-robot]

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This pull-request has been approved by: jokestax Once this PR has been reviewed and has the lgtm label, please assign shaneutt for approval. For more information see the Kubernetes Code Review Process.

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[shaneutt]

Heya :wave: I noticed this was draft, were you needing some more time for changes before reviews or did you want review while in draft?

[jokestax]

Hello,I’d appreciate a review on this draft to ensure I’m heading in the right direction before proceeding with similar changes for ICMP

[shaneutt]

Hey @jokestax! I know you updated some of the other PRs, did you need further assistance with this one? (if it's just a matter of time, no sweat just wanted to be sure to help keep you unblocked)

[shaneutt]

At this point we're going to consider this one closed due to inactivity, but we're happy to re-open it again later :+1: