Add a migration guide just in case.

Author: andriyDev

release-content/migration-guides/delete_component_access.md

@@ -0,0 +1,10 @@
+---
+title: `System::component_access` has been deleted.
+pull_requests: [19496]
+---
+
+`System::component_access` has been deleted. If you were calling this method, you can simply use
+`my_system.component_access_set().combined_access()` to get the same result.
+
+If you were manually implementing this, it should be equivalent to `System::component_access_set`
+anyway.