[CIS-5] add serde to a number of types

[lassemoldrup]

Purpose

Closes #422. Depends on https://github.com/Concordium/concordium-rust-sdk/pull/194.

Checklist

• [x] My code follows the style of this project.
• [x] The code compiles without warnings.
• [x] I have performed a self-review of the changes.
• [x] I have documented my code, in particular the intent of the hard-to-understand areas.
• [x] (If necessary) I have updated the CHANGELOG.