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

- Stack version: 8.19.19-SNAPSHOT
- 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-41285 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/46081

Latest 5 failed builds:
- https://buildkite.com/elastic/integrations/builds/46710
- https://buildkite.com/elastic/integrations/builds/46801
- https://buildkite.com/elastic/integrations/builds/46859
- https://buildkite.com/elastic/integrations/builds/46920
- https://buildkite.com/elastic/integrations/builds/47003

Start with the mongodb package's `system test: collstats` for the `collstats` data stream and review the failure from build 46081. Compare the documents produced by the test with the expected fields; done means `capped`, `freeStorageSize`, and `scaleFactor` are no longer undefined and the system test passes.

Written by the indexing model from the issue text.