chore(logging): Improve datadog logs semantic meaning warning

[gwenaskell]

Summary

The existing warning log fired when a DD reserved attribute (e.g. status) needed to be relocated based on its semantic meaning, but the destination field already existed. The message was vague — it didn't identify the source path of the semantically-tagged field, the destination it was being moved to, or which field was being renamed and why.

This PR improves the log by adding source_path, destination_path, and renamed_existing_to fields, making it actionable when triaging unexpected field renames in pipelines that route OpenTelemetry or other structured logs through the Datadog logs sink.

Vector configuration

How did you test this PR?

n/a

Change Type

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

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• 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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