Store pre-aggregated sum and value count in DocValuesSkipper

[jainankitk]

Description

This PR extends the DocValues skip index to store pre-aggregated sum and valueCount alongside the existing min/max per interval. This enables collectors and faceting operations to leverage pre-computed aggregation data at search time, avoiding the need to iterate through individual doc values.

Issue

Resolves #13870

[navneet1v]

@jainankitk will adding these new things in the docvaluesSkipper add an extra burden on the indexing side?

[sgup432]

add an extra burden on the indexing side?

I am not sure if you went through the original issue, the entire point is to store pre-aggregated data in the doc values skipper so we can take advantage of it at search time. So that it's intentional.

[navneet1v]

add an extra burden on the indexing side?

I am not sure if you went through the original issue, the entire point is to store pre-aggregated data in the doc values skipper so we can take advantage of it at search time. So that it's intentional.

Thank you. Will look into the issue.

[github-actions]

This PR has not had activity in the past 2 weeks, labeling it as stale. If the PR is waiting for review, notify the dev@lucene.apache.org list. Thank you for your contribution!

[github-actions]

This PR has not had activity in the past 2 weeks, labeling it as stale. If the PR is waiting for review, notify the dev@lucene.apache.org list. Thank you for your contribution!