Remove codegen tests with Java, move testData to boxWithJava/

There'll be a single generated test class like
BlackBoxCodegenTestGenerated

compiler/testData/codegen/boxWithJava/enum/simpleJavaEnumWithFunction.java

@@ -0,0 +1,18 @@
+package test;
+
+import java.lang.Override;
+import java.lang.String;
+
+public enum simpleJavaEnumWithFunction {
+    A {
+        @Override
+        public String repr() {
+            return "A";
+        }
+    },
+    B;
+    
+    public String repr() {
+        return "ololol" + toString();
+    }
+}