[tests] Expand coverage results

Following paths are not covered in the coverage reports for each ``:

```
./data_stream/*/lifecycle.yml
./data_stream/*/elasticsearch/ilm/*
./elasticsearch/transform/*
./kibana/tags.yml
./kibana/tag/*
./validation.yml
```

This leads to low coverage of packages inside PRs and scheduled CI runs.
Example: https://github.com/elastic/integrations/pull/14290#issuecomment-2998896369 which has 18% coverage on new code.

Increase coverage on these paths. Alternately add these paths into [exclusion list](https://github.com/elastic/integrations/blob/main/sonar-project.properties#L10) as temporary measure.

Start with sonar-project.properties, especially the exclusion list linked in the issue, and inspect how coverage reports are produced for the listed data_stream, elasticsearch, kibana, and validation.yml paths. Confirm the current behavior in a PR or scheduled CI coverage run. Done means those paths are either represented in coverage results or intentionally excluded, with the resulting coverage no longer misleading.

Written by the indexing model from the issue text.