[dga] Ensure event.kind is correctly set for pipeline errors

[MakoWish]

What does this PR do?

Modify dga integration to correctly set event.kind for pipeline errors and ensure error.message is an array.

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all data streams collect metrics or logs.
• I have added an entry to my package's changelog.yml file.
• I have verified that Kibana version constraints are current according to guidelines.

Author's Checklist

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How to test this PR locally

Related issues

• For sei: ensure packages set error.kind to "pipeline_error" in on_failure processor #6582

Screenshots

[elasticmachine]

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• Start Time: 2023-08-10T21:51:58.762+0000

• Duration: 15 min 46 sec

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[efd6]

/test

[botelastic]

Hi! We just realized that we haven't looked into this PR in a while. We're sorry! We're labeling this issue as Stale to make it hit our filters and make sure we get back to it as soon as possible. In the meantime, it'd be extremely helpful if you could take a look at it as well and confirm its relevance. A simple comment with a nice emoji will be enough :+1. Thank you for your contribution!

[MakoWish]

FYI... As a contributor, I don't have permissions to merge.

[sodhikirti07]

@elastic/ml-ui Can someone approve this PR before we merge the changes?

[peteharverson]

@alvarezmelissa87 could you have a look at this one please.

[alvarezmelissa87]

Code LGTM ⚡

[elasticmachine]

Package dga - 1.1.0 containing this change is available at https://epr.elastic.co/search?package=dga