[AO] Use kibana.alert.url instead of context.alertDetailsUrl

[maryam-saeidi]

📝 Summary

Previously, we introduced context.alertDetailsUrl in observability rules to add the URL of observability alert details there. After adding this parameter, responseOps team added a new variable to the alert document called kibana.alert.url.
In this ticket, we need to use kibana.alert.url instead of context.alertDetailsUrl and think about how to deprecate already used context.alertDetailsUrl in APM latency actions

✅ Acceptance Criteria

• Use kibana.alert.url instead of context.alertDetailsUrl
• Come up with a plan about how to deprecate context.alertDetailsUrl in APM Latency

[elasticmachine]

Pinging @elastic/actionable-observability (Team: Actionable Observability)

[maryam-saeidi]

We decided to set both kibana.alert.url and context.alertDetailsUrl for now (158391) and move to using kibana.alert.url when #158183 is implemented.