[LogsDB] [Stack 8.19.19-SNAPSHOT] [mongodb] Failing test daily: system test: collstats in mongodb.collstats

- Stack version: 8.19.19-SNAPSHOT
- LogsDB: enabled
- Package: mongodb
- Failing test: system test: collstats
- DataStream: collstats
- Owners:
- @elastic/obs-infraobs-integrations

Failure:
```
test case failed: one or more errors found in documents stored in metrics-mongodb.collstats-95064 data stream: [0] field "mongodb.collstats.stats.capped" is undefined
[1] field "mongodb.collstats.stats.freeStorageSize" is undefined
[2] field "mongodb.collstats.stats.scaleFactor" is undefined
```

First build failed: https://buildkite.com/elastic/integrations/builds/46082

Latest 5 failed builds:
- https://buildkite.com/elastic/integrations/builds/46709
- https://buildkite.com/elastic/integrations/builds/46802
- https://buildkite.com/elastic/integrations/builds/46860
- https://buildkite.com/elastic/integrations/builds/46919
- https://buildkite.com/elastic/integrations/builds/47004

Start with the mongodb integration's collstats data stream and reproduce the failing system test from the linked Buildkite failures. Inspect how the stored documents are produced and validated; done means mongodb.collstats.stats.capped, freeStorageSize, and scaleFactor are no longer undefined and the collstats system test passes.

Written by the indexing model from the issue text.