[Cases] Total event is not updated in cases documents

[christineweng]

Describe the bug:
In cases document, when attaching alerts and events, total_alert is updated correctly, while total_event remains 0

A case showing 2 alerts, 3 events and 1 comment in all casespage

In .kibana_alerting_cases, the document shows 2 alerts, 0 events and 1 comment

Kibana/Elasticsearch Stack version:
9.3/main

Functional Area (e.g. Endpoint management, timelines, resolver, etc.):
Cases

Steps to reproduce:

1. Create a case and attach some alerts and events
2. Go to Discover, create a data view called Cases, with pattern .kibana_alerting_cases*
3. Find the cases row total_events show 0 despite having events

Current behavior:
total_event does not update as number of attachments go up

Expected behavior:
total_event should reflect correct numbers

[elasticmachine]

Pinging @elastic/security-solution (Team: SecuritySolution)

[elasticmachine]

Pinging @elastic/kibana-cases (Team:Cases)