Sealed classes: extra java against kotlin tests, together with an implementation of Java diagnostics inside these tests

compiler/testData/compileJavaAgainstKotlin/sealed/Derived.java

@@ -0,0 +1,6 @@
+package test;
+
+// It's not possible to inherit from Season (it's sealed in Kotlin)
+public class Derived extends Season {
+
+}