[Stack 8.19.22-SNAPSHOT] [mongodb] Failing test daily: system test: collstats in mongodb.collstats

- Stack version: 8.19.22-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-11737 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/49549

Start with the mongodb integration's collstats system test and the documents emitted for the collstats data stream. Compare the failing fields with the integration's expected schema and test setup, then run the system test; done means the test no longer reports undefined mongodb.collstats.stats fields.

Written by the indexing model from the issue text.