Support for JDK17

Describe the bug It seems that Kryo is currently not compatible with JDK17. When calling the default constructor it fails with:

java.lang.reflect.InaccessibleObjectException: Unable to make private java.nio.DirectByteBuffer(long,int) accessible: module java.base does not "opens java.nio" to unnamed module @61322f9d
	at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:354)
	at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:297)
	at java.base/java.lang.reflect.Constructor.checkCanSetAccessible(Constructor.java:188)
	at java.base/java.lang.reflect.Constructor.setAccessible(Constructor.java:181)
	at com.esotericsoftware.kryo.unsafe.UnsafeUtil.<clinit>(UnsafeUtil.java:100)
	at java.base/java.lang.Class.forName0(Native Method)
	at java.base/java.lang.Class.forName(Class.java:467)
	at com.esotericsoftware.kryo.util.Util.<clinit>(Util.java:47)
	at com.esotericsoftware.kryo.serializers.OptionalSerializers.addDefaultSerializers(OptionalSerializers.java:38)
	at com.esotericsoftware.kryo.Kryo.<init>(Kryo.java:230)
	at com.esotericsoftware.kryo.Kryo.<init>(Kryo.java:168)

To Reproduce Kryo kryo = new Kryo();

Environment:

• JDK Version: OpenJDK 17.0.2 (Corretto-17.0.2.8.1)
• Kryo Version: 5.3.0

Additional context In my case I am also registering some standard classes. It seems to work for classes like:

• java.util.Locale
• java.time.Instant
• java.util.HashMap

But it fails for java.util.regex.Pattern due to:

java.lang.reflect.InaccessibleObjectException: Unable to make field private java.lang.String java.util.regex.Pattern.pattern accessible: module java.base does not "opens java.util.regex" to unnamed module @185a6e9

What would be the proper way to fix this?