[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/nonLiteralNull.kt

@@ -0,0 +1,17 @@
+// DONT_TARGET_EXACT_BACKEND: JS JS_IR JS_IR_ES6 WASM NATIVE
+// MODULE: lib
+// FILE: JavaClass.java
+
+class JavaClass {
+    public static String run(Runnable r) {
+        return r == null ? "OK" : "FAIL";
+    }
+}
+
+// MODULE: main(lib)
+// FILE: 1.kt
+
+fun box(): String {
+    val f: (() -> Unit)? = null
+    return JavaClass.run(f)!!
+}