Add push rules to audit events

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As part of audit events, we should log all instance-level changes in the admin panel.

We should track additions/changes to push rules on an instance:

1. Restriction toggles
2. Committer restriction
3. Reject unsigned commits
4. Do not allow users to remove git tags with git push
5. Check whether author is a GitLab user
6. Prevent committing secrets to Git
7. Commit message
8. Branch name
9. Commit author email
10. Prohibited file names
11. Max file size