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_basic2.phpt

@@ -0,0 +1,49 @@
+--TEST--
+SPL: Cloning an instance of ArrayObject which wraps an object.
+--FILE--
+<?php
+
+#[AllowDynamicProperties]
+class C { }
+
+$c = new C;
+$ao1 =  new ArrayObject($c);
+$c->p1 = 'new prop added to c before clone';
+
+$ao2 = clone $ao1;
+
+$c->p2 = 'new prop added to c after clone';
+$ao1['new.ao1'] = 'new element added to ao1';
+$ao2['new.ao2'] = 'new element added to ao2';
+var_dump($c, $ao1, $ao2);
+?>
+--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(C)#1 (3) {
+  ["p1"]=>
+  string(32) "new prop added to c before clone"
+  ["p2"]=>
+  string(31) "new prop added to c after clone"
+  ["new.ao1"]=>
+  string(24) "new element added to ao1"
+}
+object(ArrayObject)#2 (1) {
+  ["storage":"ArrayObject":private]=>
+  object(C)#1 (3) {
+    ["p1"]=>
+    string(32) "new prop added to c before clone"
+    ["p2"]=>
+    string(31) "new prop added to c after clone"
+    ["new.ao1"]=>
+    string(24) "new element added to ao1"
+  }
+}
+object(ArrayObject)#3 (1) {
+  ["storage":"ArrayObject":private]=>
+  array(2) {
+    ["p1"]=>
+    string(32) "new prop added to c before clone"
+    ["new.ao2"]=>
+    string(24) "new element added to ao2"
+  }
+}