[RCA] Improve related alerts tab in the alert details page

[maryam-saeidi]

Summary

In this PR, we added a new tab to the alert details page to show related alerts. This ticket is a follow-up to that work for implementing the following improvements:

1. Showing the number of active alerts in the tab
2. Selecting Rule name as the default group by and opening the first group
3. [Maybe] adding an event timeline to this tab (related to https://github.com/elastic/observability-dev/issues/3925)

[elasticmachine]

Pinging @elastic/obs-ux-management-team (Team:obs-ux-management)

[benakansara]

[Maybe] adding an event timeline to this tab (related to https://github.com/elastic/observability-dev/issues/3925)

I believe we have plan to include events timeline in alert details page #187112. @maciejforcone Can we show events timeline outside overview tab, so it's visible for all tabs?

[maryam-saeidi]

Thanks, @benakansara, for raising this point.

Based on my understanding, the annotations that we show in this tab would be only related alerts, to help the user understand whether these related alerts were started during the same time as the current alert or were already active and maybe less relevant. So, I guess we can have this component inside each tab, showing different events.