Consider updating diagnostic channel event names for bundled modules

https://openjs-foundation.slack.com/archives/C01QF9Q31QD/p1766166962883319

I'd like to propose that when Node.js bundles an external module that generates diagnostic_channel events, that those event names are differentiated from the upstream names. Consider undici, it generates events such as undici:request:pending-requests (https://undici.nodejs.org/#/docs/api/DiagnosticsChannel?id=undicirequestpending-requests). These events are emitted as-is from the Node.js bundled version of Undici, thus making it impossible to determine if the event was generated from the standalone module or the bundled module.

In day-to-day usage, this is not technically a problem. I am sure we can think of other cases where it might be an issue, but my current problem is that I need to retrieve the module version for the module that generated the event. I cannot currently rely on registerHooks to solve this because v20 does not support it.

Regardless, I just think it would be better to differentiate between upstream and bundled in event emissions for clarity.

Start with the linked Slack discussion and the diagnostic_channel and Undici event references in the issue. Determine a naming scheme that distinguishes bundled from standalone modules, including the Node.js v20 constraint, and define the expected event names and compatibility behavior before implementation.