[PHP 8.1] Serializable interface is deprecated

There's more usages

core9$ git grep Serializable
core/lib/Drupal/Component/Render/MarkupInterface.php:32:interface MarkupInterface extends \JsonSerializable {
core/lib/Drupal/Core/Extension/Extension.php:8: * This class does not implement the Serializable interface since problems
core/lib/Drupal/Core/Menu/MenuTreeParameters.php:15:class MenuTreeParameters implements \Serializable {
core/modules/locale/tests/src/Kernel/LocaleTranslationTest.php:24:  public function testSerializable() {
core/modules/views/src/ViewExecutable.php:21: * This class does not implement the Serializable interface since problems
core/tests/Drupal/Tests/Core/Entity/EntityTypeTest.php:515:  public function testIsSerializable() {
core/tests/Drupal/Tests/Core/Entity/EntityTypeTest.php:519:    $translation->willImplement(\Serializable::class);
core/tests/Drupal/Tests/Core/TempStore/SharedTempStoreTest.php:361:    $request->willImplement('\Serializable');

Guess kinda it, but ?string (from serialize) vs array from interface

fixed version https://wiki.php.net/rfc/custom_object_serialization

New method does not needs unserialize()

1. +++ b/core/lib/Drupal/Core/Menu/MenuTreeParameters.php
   @@ -212,6 +212,24 @@ public function excludeRoot() {
   +    return serialize(self::__serialize());
   

   Maybe a stupid question, but did you not do return serialize($this->__serialize());?

2. +++ b/core/lib/Drupal/Core/Menu/MenuTreeParameters.php
   @@ -212,6 +212,24 @@ public function excludeRoot() {
   +  public function unserialize($serialized) {
   +    foreach (unserialize($serialized) as $key => $value) {
   +      $this->{$key} = $value;
   +    }
   

   Why do we do here the same as the method __unserialize()? Can we call that method instead to do the work?

3. +++ b/core/lib/Drupal/Core/Menu/MenuTreeParameters.php
   @@ -212,6 +212,24 @@ public function excludeRoot() {
   +    return $this;
   

   Why does the method unserialize() returns $this? I get that we cannot remove this, because it will be a BC break. Just strange to me.

Please review the error I have added in the screenshot.

Thank you, fixed

All code changes look good to me.
It fixes the problem from the IS.
I could not find any other classes that implement \Serializable in core.
For me it is RTBC.

Committed 4d2631d and pushed to 9.3.x. Thanks!