Use SerDes for H2 storage of retained messages

[andsel]

Release notes

[rn:skip]

What does this PR do?

Switch serializer of Retained messages in H2 store to also handle MQTT properties.
Implement a new H2 DataType for Retained Message.

Why is it important/What is the impact to the user?

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] I have made corresponding change to the default configuration files (and/or docker env variables)
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] I have updated the Changelog if it's a feature or a fix that has to be reported

Author's Checklist

• [ ]

How to test this PR locally

Related issues

• Relates Payload format verification and content type properties handling #826

Use cases