Fix upgrade test; correct/add APIs

[JordanMartinez]

Description of the change

Main focus of this PR was re-enabling the upgrade test I disabled temporarily in #48 by using Aff.

Along the way, I realized that the socket types should be upgraded to Socket TCP because (at least AFAICT) we don't expose a way to provide a different class than Socket. I also noticed that the ClientRequest type was missing its close event handler.

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Checklist:

• Added the change to the changelog's "Unreleased" section with a reference to this PR (e.g. "- Made a change (#0000)")
• Linked any existing issues or proposals that this pull request should close
• Updated or added relevant documentation
• Added a test for the contribution (if applicable)