make template_enricher support Prometheus Alert annotations

[zmx]

Is your feature request related to a problem? We have some third-party PrometheusRules having runbook URL in annotations

Describe the solution you'd like Make template_enricher could annotate with PrometheusRules annotations

Describe alternatives you've considered Static/Custom template_enrich configs

Additional context There are previous discussion/request in https://robustacommunity.slack.com/archives/C02R0LVANKY/p1708600339808769

https://github.com/robusta-dev/robusta/blob/67c77644516af5a19cab7ccb8fce54f6197002ab/playbooks/robusta_playbooks/alerts_integration.py#L331

 if isinstance(event, PrometheusKubernetesAlert):
        labels.update(event.alert.labels)
        labels.update(event.alert.annotations)