Update hux service definition for social_post

Problem/Motivation

The current implementation for social_posts.form.hooks service is not following the correct approach for service auto wiring

https://github.com/goalgorilla/open_social/blob/main/modules/social_feat...

Steps to reproduce

N/A

Proposed resolution

Update the service definition following Drupal examples:

• https://www.drupal.org/node/3323122 →
• https://www.drupal.org/node/3218156 →

Remaining tasks

User interface changes

API changes

Data model changes