[Response Ops][Maintenance Window] Fix MW bug where rules that generate multiple alerts only has 1 alert that gets muted

[JiaweiWu]

Summary

Issue: #190750

Fix a bug with maintenance window where only 1 alert from a rule that generates multiple alerts has the maintenance window ID associated. The fix was to remove a size field (not sure why that was there).

To verify:

1. Create an active maintenance window with conditional filter
2. Create a rule that matches the maintenance window filter and let it generate multiple alerts (I use ES query rule on the task_manager index with runAt as timefield. Then use groupBy on the runAt field.).
3. Assert that all of the alerts generated have the maintenance window ID associated with it

Checklist

• Unit or functional tests were updated or added to match the most common scenarios

[elasticmachine]

Pinging @elastic/response-ops (Team:ResponseOps)

[ersin-erdal]

LGTM
Tested locally, works as expected

[JiaweiWu]

@elasticmachine merge upstream

[kibana-ci]

💛 Build succeeded, but was flaky

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• Commit: 48c372d

Failed CI Steps

Metrics [docs]

✅ unchanged

History

• 💚 Build #228739 succeeded 8a36687

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@elasticmachine merge upstream