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___construct_basic7.phpt

@@ -0,0 +1,35 @@
+--TEST--
+SPL: ArrayObject::__construct: Using object with shared properties
+--FILE--
+<?php
+$y = 2;
+$x = 1;
+$a = array($y, $x);
+$o = (object)$a;
+$ao = new ArrayObject($o);
+$ao->asort();
+var_dump($a, $o, $ao);
+?>
+--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
+array(2) {
+  [0]=>
+  int(2)
+  [1]=>
+  int(1)
+}
+object(stdClass)#1 (2) {
+  ["1"]=>
+  int(1)
+  ["0"]=>
+  int(2)
+}
+object(ArrayObject)#2 (1) {
+  ["storage":"ArrayObject":private]=>
+  object(stdClass)#1 (2) {
+    ["1"]=>
+    int(1)
+    ["0"]=>
+    int(2)
+  }
+}