Docs: reorganize documentation for querying traces

Our documentation for querying traces needs some love. Some good resources to reference:
* General good advice for docs: https://diataxis.fr/
* Micromegas: an observability platform with excellent SQL docs:
* Reference: https://madesroches.github.io/micromegas/docs/query-guide/schema-reference/
* Examples: https://madesroches.github.io/micromegas/docs/query-guide/query-patterns/
* More examples: https://madesroches.github.io/micromegas/docs/query-guide/async-performance-analysis/
* Performance guide: https://madesroches.github.io/micromegas/docs/query-guide/performance/

Start by reviewing the current documentation for querying traces, then compare its organization with the linked Diátaxis guidance and Micromegas schema, examples, and performance pages. Done means the trace-query documentation has a clearer structure and covers reference, examples, and performance guidance.

Written by the indexing model from the issue text.