[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/sam/kt11519Constructor.kt

@@ -0,0 +1,43 @@
+// DONT_TARGET_EXACT_BACKEND: JS JS_IR JS_IR_ES6 WASM NATIVE
+// SKIP_JDK6
+// MODULE: lib
+// FILE: Custom.java
+
+class Custom<K, V> {
+    public interface MBiConsumer<T, U> {
+        void accept(T t, U u);
+    }
+
+    private K k;
+
+    private V v;
+
+    public Custom(K k, V v) {
+        this.k = k;
+        this.v = v;
+    }
+
+    public void forEach(MBiConsumer<? super K, ? super V> action) {
+        action.accept(k, v);
+    }
+}
+
+// MODULE: main(lib)
+// FILE: 1.kt
+
+import java.util.Arrays
+
+fun box(): String {
+    val instance = Custom<String, String>("O", "K")
+    var result = "fail"
+    instance.forEach (Custom.MBiConsumer<String, String> { a, b ->
+        result = a + b
+    })
+
+    val superInterfaces = Arrays.toString((Class.forName("_1Kt\$box$1")).genericInterfaces)
+    if (superInterfaces != "[Custom\$MBiConsumer<java.lang.String, java.lang.String>]") {
+        return "fail: $superInterfaces"
+    }
+
+    return result
+}