Audit Log: Datadog & Splunk

[sudomateo]

Document how to send audit logs to Datadog and Splunk, the most popular logging platforms for large enterprises. Here are the requirements.

• A user on our docs site can search (i.e., Ctrl+K) for "Datadog" or "Splunk" and find this document.
• Push an example to oxidecomputer/showcase so other users can find it and use it.

I think the best way to handle this is to either:

1. Update the existing Audit Log document with the schema and examples to send to Datadog and Splunk.
2. Make Audit Log a new section and have nested sections for "Overview" and "Export Audit Logs".
3. Update the existing OpenTelemetry document with the audit log schema and examples to send to Datadog and Splunk.