Add a user permission to restrict access to AI suggestion generation

Problem/Motivation

Currently, any user that can edit the node can generate AI suggestions for the reference fields. This is not ideal since AI suggestions incur a cost.

Example Use Case:
On a moderated site, there could be user roles with lower access that can only create and edit content for review. You may not want the lower level user roles to constantly generate suggestions since AI usage incurs a cost. In this scenario, you may want only the user that can publish the content to be able to generate the suggestions.

Proposed resolution

• Add a user permission for "Access AI Auto-reference suggestion tools". The AI Content Suggestions have a similar permission for "Access AI Content suggestion tools".
• Use the new permission to restrict access to the AI suggestions.

Remaining tasks

• Create a PR
• Update any documentation

User interface changes

None.

API changes

None.

Data model changes

None.