Move ir box test under "box/ir"

compiler/testData/codegen/box/ir/closureConversion/innerClass2.kt

@@ -0,0 +1,7 @@
+class Outer(val x: String) {
+    inner class Inner(val y: String) {
+        val z = x + y
+    }
+}
+
+fun box() = Outer("O").Inner("K").z