Improve tests for JDK 17

[theigl]

This PR attempts to fix as many tests as possible when running under JDK17 without any add-opens arguments.

Most tests work without opening up modules now. Only one tests still fails:

• SerializationCompatTest fails because of AtomicInteger.

We need custom serializers for Atomic* JDK classes to fix this.

[theigl]

I added a fall-back for lambda deserialization in f3cd2df.

[theigl]

The only remaining issue is with AtomicInteger and we can't fix this without breaking backwards compatibility. We should add serializers for Atomic*, UUID, Pattern etc in Kryo 6.