[Serverless] Remove cobra dependency

[maxday]

What does this PR do?

I think we can get rid of Cobra as we never use the extension as a CLI + get the version
The version is logged when the extension is starting

This PR also removes imports from expvar and net/http/pprof as we do not use them

Motivation

Cleanup

Describe how to test/QA your changes

integration tests to make sure that the extension keeps starting

Reviewer's Checklist

• If known, an appropriate milestone has been selected; otherwise the Triage milestone is set.
• Use the major_change label if your change either has a major impact on the code base, is impacting multiple teams or is changing important well-established internals of the Agent. This label will be use during QA to make sure each team pay extra attention to the changed behavior. For any customer facing change use a releasenote.
• A release note has been added or the changelog/no-changelog label has been applied.
• Changed code has automated tests for its functionality.
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• At least one team/.. label has been applied, indicating the team(s) that should QA this change.
• If applicable, docs team has been notified or an issue has been opened on the documentation repo.
• If applicable, the need-change/operator and need-change/helm labels have been applied.
• If applicable, the config template has been updated.

[nhinsch]

🌮