[Test] Properly merge box against java testdata into codegen/box

Previous commit about it was 3199ce03 and it was completely wrong

compiler/testData/codegen/box/notNullAssertions/delegation.kt

@@ -0,0 +1,36 @@
+// DONT_TARGET_EXACT_BACKEND: JS JS_IR JS_IR_ES6 WASM NATIVE
+// IGNORE_BACKEND_FIR: JVM_IR
+
+// MODULE: lib
+// FILE: Delegation.java
+
+public class Delegation {
+    public static class ReturnNull {
+        public String foo() {
+            return null;
+        }
+    }
+}
+
+// MODULE: main(lib)
+// FILE: delegation.kt
+
+interface Tr {
+    fun foo(): String
+}
+
+class DelegateTo : Delegation.ReturnNull(), Tr {
+    override fun foo() = super<Delegation.ReturnNull>.foo()
+}
+
+class DelegateFrom : Tr by DelegateTo()
+
+fun box(): String {
+    try {
+        DelegateFrom().foo()
+        return "Fail: should have been an exception"
+    }
+    catch(e: NullPointerException) {
+        return "OK"
+    }
+}