[Test] Move KotlinAgainstKotlin tests under BlackBoxCodegen tests

compiler/testData/codegen/box/compileKotlinAgainstKotlin/classInObject.kt

@@ -0,0 +1,20 @@
+// MODULE: lib
+// FILE: A.kt
+
+package a
+
+object CartRoutes {
+    class RemoveOrderItem {
+        val result = "OK"
+    }
+}
+
+// MODULE: main(lib)
+// FILE: B.kt
+
+import a.CartRoutes
+
+fun box(): String {
+    val r = CartRoutes.RemoveOrderItem()
+    return r.result
+}