Add audit event to CreateRunnerService

What does this MR do and why?

This MR reinstates !173885 (merged) which was reverted as part of an incident response. It adds an audit event to CreateRunnerService.

• Changelog: added
• EE: true

References

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• Add audit event to CreateRunnerService (!173885 - merged)
• 2024-12-11: Runner registration returning 500 e... (gitlab-com/gl-infra/production#18984 - closed)
• Add audit event when runner is created (#506385 - closed)

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