Add OpenTelemetry Tracing

[htdvisser]

Summary

In https://github.com/TheThingsNetwork/lorawan-stack/pull/5642 I started adding OpenTelemetry trace regions to pkg/identityserver/bunstore. We should instrument more code in other packages, and set up exporters and such.

Current Situation

We have some OpenTelemetry instrumentation in pkg/identityserver/bunstore, but the rest of the OpenTelemetry SDK has not been set up.

Why do we need this? Who uses it, and when?

OpenTelemetry tracing is going to be useful for getting more insights into how messages pass trough The Things Stack and can help us understand how one component affects others, especially as the system grows.

Proposed Implementation

• Instrument more code with OpenTelemetry trace spans (docs)
• Set up the OpenTelemetry SDK (docs)

Contributing

• [ ] I can help by doing more research.
• [ ] I can help by implementing the feature after the proposal above is approved.
• [ ] I can help by testing the feature before it's released.

Code of Conduct

• [X] I agree to follow TTN's Community Code of Conduct.