Update documentation to take advantage of ExtendedConfigKey data

[Claudenw]

Requires #515
Requires aiven-commons publication.

aiven-commons has a module to provide velocity beans for Kafka ConfigKey and ExtendedConfigKey data. This change is to use those libraries to create the documentation for the configurations.

This will involve

• Replace the site calls to the classes found int site /src to the aiven-commons versions.