Support Zipkin Client/Server Spans

[joe-elliott]

Is your feature request related to a problem? Please describe.
According to the Zipkin spec the client and server spans should share the same id:
https://zipkin.io/zipkin/2.11.3/zipkin/zipkin2/Span.html#shared--

When an RPC trace is client-originated, it will be sampled and the same span ID is used for the server side. However, the server shouldn't set span.timestamp or duration since it didn't start the span.

This breaks the Grafana UI b/c it does not expect two spans to have the same ID.

Describe the solution you'd like
Dedupe span IDs on query. Here is sample code from Jaeger:

https://github.com/jaegertracing/jaeger/blob/master/model/adjuster/span_id_deduper.go#L24