Make module D11 ready

Problem/Motivation

As Drupal 11 development progresses, modules need to be updated to ensure compatibility with the new core version. This issue serves as a meta task to track the necessary work for making the HTTP/2 Server Push module (http2_server_push) fully compatible with Drupal 11.

Maintaining compatibility ensures that users can seamlessly upgrade their Drupal sites while continuing to use this module's functionality.