[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/annotations/retentionInJava.kt

@@ -0,0 +1,20 @@
+// DONT_TARGET_EXACT_BACKEND: JS JS_IR JS_IR_ES6 WASM NATIVE
+// MODULE: lib
+// FILE: Foo.java
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+@Retention(RetentionPolicy.CLASS)
+@interface Foo {
+}
+
+// MODULE: main(lib)
+// FILE: 1.kt
+
+@Foo class Bar
+
+fun box(): String {
+    Bar()
+    return "OK"
+}