[Workflow] Mark registry as internal and deprecate the service

Instead, all workflow services are tagged and can be injected with the
following YAML syntax:

```yaml
!tagged_locator  { tag: workflow, index_by: name }
```

or PHP syntax:

```php
tagged_locator('workflow', 'name')
```

Also, two others tags exists for each workflow types
* `workflow.workflow`
* `workflow.state_machine`

Author: lyrixx

CHANGELOG.md

@@ -1,6 +1,11 @@
 CHANGELOG
 =========
 
+6.2
+---
+
+ * Mark `Symfony\Component\Workflow\Registry` as internal
+
 6.0
 ---
 

Registry.php

@@ -17,6 +17,8 @@
 /**
  * @author Fabien Potencier <[email protected]>
  * @author Grégoire Pineau <[email protected]>
+ *
+ * @internal since Symfony 6.2. Inject the workflow where you need it.
  */
 class Registry
 {