Merge boxWithStdlib testData into box, delete BoxWithStdlib test

compiler/testData/codegen/box/jvmStatic/privateMethod.kt

@@ -0,0 +1,16 @@
+// WITH_RUNTIME
+
+object A {
+
+    private @JvmStatic fun a(): String {
+        return "OK"
+    }
+
+    object Z {
+        val p = a()
+    }
+}
+
+fun box(): String {
+    return A.Z.p
+}