[content/en/opentelemetry] Mention different signals request different batch processor configs

[songy23]

What does this PR do?

Remind the readers that they may need different batch sizes for batch processor for different signal types (traces/metrics/logs) when using datadog exporter.

Motivation

The previous comment and config in the batch processor only refers to the payload size limit of trace intake. When customers use the same config for metrics or logs pipeline, they may get 413 errors because metrics and logs have a smaller payload size limit than that in trace. This led to customer confusions and issues being filed in https://github.com/open-telemetry/opentelemetry-collector-contrib.

Additional Notes

Related customer issues:

• Log export fails with '413 Request Entity Too Large' status code open-telemetry/opentelemetry-collector-contrib#16834
• [exporter/datadog] metrics exporter: 413 - Request Entity Too Large  open-telemetry/opentelemetry-collector-contrib#17566

Also note that the payload size limits in metrics and logs intake are in the public document, but traces intake doesn't have a public reference.

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Reviewer checklist

• Review the changed files.
• Review the URLs listed in the Preview section.
• Check images for PII
• Review any mentions of "Contact Datadog support" for internal support documentation.

[github-actions]

Preview links (active after the build_preview check completes)

Modified Files

• https://docs-staging.datadoghq.com/songy23/otel-collector-batch-config/opentelemetry/otel_collector_datadog_exporter

[songy23]

Thanks for the review!