Spring Cloud Netflix Add metrics for Euereka server events

Add metrics (Micrometer-based) listener for EurekaInstanceRegisteredEvent, EurekaInstanceRenewedEvent, EurekaInstanceCanceledEvent. Part of Spring projects observability review.

Comment From: heowc

hello. I recently did some related PR.

Can I understand this issue as collecting the number of events over a certain period of time?

Comment From: OlgaMaciaszek

Thanks, @heowc. I think your PR actually covers this issue. Closing with https://github.com/spring-cloud/spring-cloud-netflix/pull/4270.