tracking: 4.12.x special LTS backporting

[runspired]

This ticket tracks work we expect to backport to 4.12, including that mentioned here https://blog.emberjs.com/ember-data-4-12-special-release-update-2023-09-22

• [ ] @ember-data/rest builder utils
• [ ] @ember-data/active-record builder utils
• [ ] @ember-data/request-utils
• [ ] @ember-data/json-api/request (potentially as @ember-data/json-api-request) builder utils
• [ ] CacheHandler updates
• [x] RequestManager updates
• [ ] removal of @ember/runloop usage