Opentelemetry OTLP support

[joepio]

We already have support for Jaeger using opentelemetry_rust, but not yet for other opentelemetry implementations like OpenObserve. Would be nice to switch to OTLP. We could probably ditch opentelemetry_jaeger and only use opentelemetry_otlp.

However, I had some issues while implementing. I need an HTTP client like hyper or reqwest. Not a lot of docs for this. I think I'm close though.

PR Checklist:

• Link to related issues: #number
• Add changelog entry linking to issue, describe API changes
• Add tests (optional)
• (If new feature) add to description / readme