Added serde derive to close reason and close code

[LucaCappelletti94]

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PR Type

Feature

PR Checklist

• [x] ~Tests for the changes have been added / updated.~
• [x] ~Documentation comments have been added / updated.~
• [x] A changelog entry has been made for the appropriate packages.
• [x] Format code with the latest stable rustfmt.
• [x] (Team) Label with affected crates and semver status.

Overview

Added feature-gated support for serde::Serialize and serde::Deserialize to CloseReason and CloseCode

Closes #3578