Enable nginx workload tracing

### Enhancement Proposal

We can configure the coordinator workload (nginx) to generate and export traces to an otel-compatible tracing backend.
For nginx to be able to generate traces about incoming requests, it needs the [`ngx_otel_module`](https://nginx.org/en/docs/ngx_otel_module.html).

Context: https://github.com/canonical/nginx-rock/issues/30

Now we can:
- [ ] use it in tempo
- [ ] use it in pyroscope
- [ ] loki
- [ ] mimir

Start with the coordinator workload configuration and read the linked nginx-rock issue #30, then investigate how ngx_otel_module can generate and export traces to an OTEL-compatible backend. Done means the nginx workload can emit traces and the supported integrations listed in the issue—Tempo, Pyroscope, Loki, and Mimir—are addressed or their compatibility is documented.

Written by the indexing model from the issue text.