docs: Update live queries documentation with new response format

[KishoreKicha14]

Description

Update the live queries API documentation to reflect the restructured response model in the query-insights plugin. Changes include:

• Updated response format to match the new LiveQueryRecord model with coordinator_task and shard_tasks breakdowns replacing the old flat measurements structure
• Documented new query parameters: wlmGroupId for workload management group filtering and use_finished_cache for including recently completed queries
• Added a detailed "Finished queries cache" section covering the full cache lifecycle (lazy activation, idle timeout auto-deactivation, self-healing reactivation) and the search.insights.live_queries.cache.idle_timeout cluster setting
• Added field-by-field explanations of the live query response (top-level summary, coordinator task, shard tasks) and finished query response (id correlation, top_n_id linkage)
• Updated all response field tables to match the current code

Issues Resolved

Closes[]

Version

3.6

Frontend features

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Checklist

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[kolchfa-aws]

@KishoreKicha14 Is this ready for doc review?

[kolchfa-aws]

Thank you, @KishoreKicha14! Doc review complete.