Merge boxWithStdlib testData into box, delete BoxWithStdlib test

compiler/testData/codegen/box/jvmOverloads/companionObject.kt

@@ -0,0 +1,14 @@
+// WITH_RUNTIME
+
+class C {
+    companion object {
+        @JvmStatic @kotlin.jvm.JvmOverloads public fun foo(o: String, k: String = "K"): String {
+            return o + k
+        }
+    }
+}
+
+fun box(): String {
+    val m = C::class.java.getMethod("foo", String::class.java)
+    return m.invoke(null, "O") as String
+}