Auditing for changes to event streaming destinations

What does this MR do and why?

• Adds audit events for adding, deleting and updating audit streaming destinations.
• Updates documentation.

Screenshots

How to set up and validate locally

• Create a group.
• Create an audit event streaming destination. (https://docs.gitlab.com/ee/administration/audit_event_streaming.html#add-a-new-event-streaming-destination)
• Change an audit event streaming desination.
• Destroy an audit event streaming destination.
• View the audit events for the group.
• Assert that the events have been created succesfully and accurately.

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 #344664 (closed)