[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/adapters/simplest.kt

@@ -0,0 +1,18 @@
+// DONT_TARGET_EXACT_BACKEND: JS JS_IR JS_IR_ES6 WASM NATIVE
+// MODULE: lib
+// FILE: JavaClass.java
+
+class JavaClass {
+    public static void run(Runnable r) {
+        r.run();
+    }
+}
+
+// MODULE: main(lib)
+// FILE: 1.kt
+
+fun box(): String {
+    var v = "FAIL"
+    JavaClass.run { v = "OK" }
+    return v
+}