[DOCS-11944] Add Node.js examples and non-JSON log correlation for OTel traces

[brett0000FF]

What does this PR do? What is the motivation?

Fixes DOCS-11944

Adds Node.js examples and non-JSON log format support to the OpenTelemetry trace-log correlation page:

• New Node.js tab in the "Inject trace context into your logs" section, showing how to use @opentelemetry/instrumentation-winston for automatic trace context injection.
• New "Non-JSON logs" sub-section under "Scrape logs from files", with a Node.js/Winston example for manual context injection into plain text logs and a corresponding filelog receiver config using regex_parser.

References

• OTel spec: Trace Context in Non-OTLP Log Formats
• @opentelemetry/instrumentation-winston
• @opentelemetry/instrumentation-pino
• Example: OTel Node.js trace context injection

Merge instructions

Merge readiness:

• Ready for merge

Additional notes

Based on customer feedback requesting guidance for Node.js apps with non-JSON log formats.

[github-actions]

Preview links (active after the build_preview check completes)

Modified Files

• https://docs-staging.datadoghq.com/brett.blue/DOCS-11944-nodejs-non-json-trace-correlation/tracing/other_telemetry/connect_logs_and_traces/opentelemetry

[billmeyer]

It's slightly confusing while reading through the doc- of the 3 language choices: Go, Java, Node.js that are presented, when the reader scrolls down to the JSON logs example, the language shifts to Python for that one example and then back to Node.js for the Non-JSON logs. It would be good to stay consistent with the examples throughout.

Also, the Python examples looks suspect to me. When logging as JSON log lines, I would expect to simply use an add_fields method so that the log line is written as JSON and no additional, manual parsing is needed.

[brett0000FF]

@billmeyer - Thanks for the review! Great points about the page overall.

The Python examples in the JSON logs and OTLP sections are pre-existing content, and this PR only added the Node.js tab at the top and the new Non-JSON logs subsection at the bottom.

The language inconsistency you're seeing was already there before this PR: Go/Java at the top, Python in the middle. My changes made it more noticeable by adding Node.js to the top tabs.

Looking at this more broadly, there's a bigger structural question here: OTel is treated as a "language" tab alongside Go, Java, Node.js, etc. on the parent page. This needs to be totally restructured with language first, then Datadog vs. OTel. That would eliminate the mixed-language examples problem entirely.

But that's a significant restructure, so I'll create another ticket to tackle that. 🫡