Adds audit events for ML Models file creation and deletion

What does this MR do and why?

Adds audit events for ML Models

Customers need to audit when models are created or destroyed for regulatory reasons

Changelog: added

How to set up and validate locally

1. Navigate to a Project, then 'Deploy > Model registry'

2. Click on 'Create model'

3. Create a model and model version with an uploaded file

4. Delete the file

5. With gdk psql, run the following query:

   select * from audit_events order by created_at desc;

   You should see events for model file addition and removal

Related to #463215 (closed)