[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/differentFqNames.kt

@@ -0,0 +1,22 @@
+// IGNORE_BACKEND_FIR: JVM_IR
+// DONT_TARGET_EXACT_BACKEND: JS JS_IR JS_IR_ES6 WASM NATIVE
+// WITH_RUNTIME
+// MODULE: lib
+// FILE: Custom.java
+
+class Custom {
+    public interface Runnable {
+        void run2();
+    }
+}
+
+// MODULE: main(lib)
+// FILE: 1.kt
+
+fun box(): String {
+    val f = { }
+    val class1 = Runnable(f).javaClass
+    val class2 = Custom.Runnable(f).javaClass
+
+    return if (class1 != class2) "OK" else "Same class: $class1"
+}