Merge boxWithJava testData into box, delete BoxWithJava test

compiler/testData/codegen/box/statics/kt8089.kt

@@ -0,0 +1,21 @@
+class C {
+    companion object {
+        private val s: String
+        private var s2: String
+
+        init {
+            s = "O"
+            s2 = "O"
+        }
+
+        fun foo() = s
+
+        fun foo2() = s2
+
+        fun bar2() { s2 = "K" }
+    }
+}
+
+fun box(): String {
+    return C.foo() + {C.bar2(); C.foo2()}()
+}