Improve use of tracing spans in query path

The purpose of this issue is to get a better understanding of how `influxdb3` uses trace spans in the query path.

To better help diagnose and troubleshoot latency and performance issues in the query path, we may need to better leverage tracing spans in the query path, as what we have seen in results from the perf team, the information we are generating is sparse.

### Objectives of this issue

1. analyze generated trace spans during query execution to see what information is being generated
2. determine which is being generated from `iox_query` and which is generated from this codebase
3. determine if there are any obvious gaps in that information
4. propose follow-up work