[Feature Request] Support pre-aggregated data in Star Tree

[sarthakaggarwal97]

Is your feature request related to a problem? Please describe

Coming here from this: #14512 (comment)

There are cases where the users would want to ingest already aggregated data by specifying the _doc_count field. This way, during star-tree aggregation, we can account for the number of documents while calculating accurate metrics.

Describe the solution you'd like

Support for pre-aggregated data with Star Tree

Related component

Indexing:Performance

Describe alternatives you've considered

No response

Additional context

https://opensearch.org/docs/2.4/opensearch/bucket-agg/#account-for-pre-aggregated-data

[mgodwan]

[Indexing Triage Meeting 07/22]

@sarthakaggarwal97 Thanks for filing this. Please tag the issue with the release you're targeting this for.

[bharath-techie]

#15288 -- with _doc_count support changes, we should solve this as well. so closing this.