[FEATURE] Move exporter config to Query Insights level

[ansjcy]

Is your feature request related to a problem?

Currently, we have different exporters config for different metrics.
https://opensearch.org/docs/latest/observing-your-data/query-insights/top-n-queries/#configuring-a-local-index-exporter
This is not a good pattern since we don't have specific use cases when users enabled multiple top n metrics, but they only want to exporter certain of them.

What solution would you like?

Instead of search.insights.top_queries.latency.exporter.type, and search.insights.top_queries.delete_after_days
we should do search.insights.top_queries.exporter.type and search.insights.top_queries.exporter.delete_after_days

What alternatives have you considered?

A clear and concise description of any alternative solutions or features you've considered.

Do you have any additional context?

Add any other context or screenshots about the feature request here.

[ansjcy]

This is fixed in #210