Re-implementing tracing with diagnostics_channel and AsyncResource

[rochdev]

Node has had these features for a while and I think it would be worth it to re-implement Moleculer's tracing on top of them. This would have the benefit of decoupling the instrumentation from tracing, and it would enable APM vendors like Datadog or standards like OpenTelemetry to use the events instead of having to monkey-patch the library.

Basically, diagnostics_channel can be used to publish diagnostics information globally, and AsyncResource can be used to keep track of asynchronous operations so that each operation runs in the right continuation context.

I don't have time to open a PR for it right now but I thought I would at least throw the idea out there to see what others think. We've already decoupled the instrumentation from tracing in dd-trace, and this is what it currently looks like:

• Instrumentation: https://github.com/DataDog/dd-trace-js/tree/de10b4315f7f5a92acd4db46925ed768dd20353f/packages/datadog-instrumentations/src/moleculer
• Tracing: https://github.com/DataDog/dd-trace-js/tree/de10b4315f7f5a92acd4db46925ed768dd20353f/packages/datadog-plugin-moleculer/src

On the Datadog side, we are also exploring adding more of these events to dd-trace which could further simplify the Datadog exporter from Moleculer, although I'd probably suggest instead to focus the effort for built-in tracing to OpenTelemetry since it already has exporters for most vendors (already being discussed in #1062).