Refactored audit event for group creation

What does this MR do and why?

This MR is refactoring code for logging audit events for group creation and moving to method Auditor.audit as part of &8572.

Screenshots or screen recordings

Audit event received at streaming destination:

**Audit event on GitLab dashboard **

How to set up and validate locally

1. Setup an external http destination for streaming audit events to external destinations by following https://docs.gitlab.com/ee/administration/audit_event_streaming/, preferably on group level.
2. Create a subgroup inside the group where you added above destination.
3. Once the subgroup is created, check the external destination and it should have received an audit event with event_type as group_created.

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 #411595 (closed)