JSON support for Java 16+ Records

[joakime]

Jetty version(s)
Jetty 12

Enhancement Description
More and more JSON libs are supporting the serialization in/out of Java Record types.
We should support it too.

[joakime]

See google/gson#2201

[github-actions]

This issue has been automatically marked as stale because it has been a
full year without activity. It will be closed if no further activity occurs.
Thank you for your contributions.

[sbordet]

Implemented in #12628.