[DowngradePhp81] Add DowngradeArrayIsListRector

[samsonasik]

Php 8.1 has new function array_is_list() which can be downgraded to :

-array_is_list([1 => 'apple', 'orange']);
+$arrayIsList = function (array $array) : bool {
+    if (function_exists('array_is_list')) {
+        return array_is_list($array);
+    }
+    if ($array === []) {
+        return true;
+    }
+    $current_key = 0;
+    foreach ($array as $key => $noop) {
+        if ($key !== $current_key) {
+            return false;
+        }
+        ++$current_key;
+    }
+    return true;
+};
+$arrayIsList([1 => 'apple', 'orange']);

ref https://php.watch/versions/8.1/array_is_list#array_is_list-polyfill

[samsonasik]

All checks have passed 🎉 @TomasVotruba it is ready for review.

[TomasVotruba]

Thank you 👍