Add an entity usage api

Problem/Motivation

The entity usage module → provides an API to to track and expose entity relationships in Drupal.

There are several issues with the current file usage and file_get_file_references and having a generic entity usage API would help resolve some of these issues.

Proposed resolution

• Bring entity usage API into core.
• Deprecate file usage service
• Use entity usage instead of file_get_file_references in the File access control handler.

Remaining tasks

• Agree on approach
• Implement
• Review