Add project push rules changes auditor

What does this MR do and why?

What

Add project push rules changes auditor

Note: only supports Reject unverified users (next iteration will support other types) as we want to get this out right away to support #268116

Why

• Audit push rule changes at the project level
• Setup base push rule changes auditor in preparation for instance level push rule changes auditor

Screenshots or screen recordings

Admin Audit Logs

Streaming Audit Logs

Streamed JSON Example

{
   "id":152,
   "author_id":1,
   "entity_id":31,
   "entity_type":"Project",
   "details":{
      "change":"reject unverified users",
      "from":true,
      "to":false,
      "target_details":"main-dev-group/push-rules",
      "author_name":"Administrator",
      "author_class":"User",
      "target_id":4,
      "target_type":"PushRule",
      "custom_message":"Changed reject unverified users from true to false",
      "ip_address":"172.16.123.1",
      "entity_path":"main-dev-group/push-rules"
   },
   "ip_address":"172.16.123.1",
   "author_name":"Administrator",
   "entity_path":"main-dev-group/push-rules",
   "target_details":"main-dev-group/push-rules",
   "created_at":"2023-09-20T03:07:19.395Z",
   "target_type":"PushRule",
   "target_id":4,
   "event_type":"project_push_rules_commit_committer_check_updated"
}

How to set up and validate locally

1. Navigate to a project
2. Navigate to Settings > Repository > Push rules
3. Check/uncheck Reject unverified users
4. Verify that the audit event appears

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #268116