feat(opentelemetry source): Support per-signal OTLP decoding config

[pront]

Summary

Allow independent configuration of OTLP decoding for logs, metrics, and traces. Maintains backward compatibility with boolean configuration.

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Vector configuration

How did you test this PR?

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

• Closes: feat(opentelemetry source): Support per-signal use_otlp_decoding configuration #24455

Notes

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[pront]

/ci-run-e2e-opentelemetry-logs

[pront]

/ci-run-e2e-opentelemetry-logs

[datadog-vectordotdev]

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

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[thomasqueirozb]

Looks good. Thanks!