Currently we generate Java 8 bytecode for everything, including tests. As a result, our Java 13/14 CI jobs do not really test JDK13/14, since they use Java 8 bytecode.

This is especially important for testing bytecode enhancement, which may be affected by different bugs depending on the version of the bytecode.

For example, the JDK14 job is currently succeeding, even though we're using an outdated version of bytebuddy that doesn't support Java 14 bytecode.