feat(datadog_logs): Emit warn logs for misconfigured reserved attributes

[20agbekodo]

Summary

Modify the datadog_logs destination configuration to emit WARN logs when there are missing reserved Datadog attribute fields. This change is necessary to improve logging and alert on potential issues with malformed logs.

Vector configuration

How did you test this PR?

Change Type

• Bug fix
• New feature
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• [ X ] No

Does this PR include user facing changes?

• [ X ] Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the no-changelog label to this PR.

References

Notes

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