ext/spl: Deprecate ArrayObject and ArrayIterator with objects (#19420)

RFC: https://wiki.php.net/rfc/deprecations_php_8_5#deprecate_arrayobject_and_arrayiterator_with_objects

This also moves tests into a subfolder.

ext/spl/tests/ArrayObject/ArrayObject_clone_other_std_props.phpt

@@ -0,0 +1,24 @@
+--TEST--
+Clone ArrayObject using other with STD_PROP_LIST
+--FILE--
+<?php
+
+$a = new ArrayObject([1, 2, 3], ArrayObject::STD_PROP_LIST);
+$b = new ArrayObject($a);
+$c = clone $b;
+var_dump($c);
+
+?>
+--EXPECTF--
+Deprecated: ArrayObject::__construct(): Using an object as a backing array for ArrayObject is deprecated, as it allows violating class constraints and invariants in %s on line %d
+object(ArrayObject)#3 (1) {
+  ["storage":"ArrayObject":private]=>
+  array(3) {
+    [0]=>
+    int(1)
+    [1]=>
+    int(2)
+    [2]=>
+    int(3)
+  }
+}