feat(plugin/packetparser): identify CPU as Flow metadata

[hainenber]

Description

Add CPU number as Flow metadata

Related Issue

Closes #94

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• [ ] I have tested the changes locally.
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• [x] I have added tests, if applicable.

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[hainenber]

Thanks for the PR. Can you add Testing Done section, especially testing around verifying the CPU variable is correct?

Sure, I'll try get the cluster up and running for a proper E2E test. I was thinking that unit test would be sufficient 😅