SOLR-18195: Support for Collapse Results in Combined Query Component

[ercsonusharma]

https://issues.apache.org/jira/browse/SOLR-18195

With reference to previous new Query Component Feature: https://issues.apache.org/jira/browse/SOLR-17319

Description

When using {!collapse} with CombinedQueryComponent (hybrid search / RRF), duplicate documents appear in the result set for the same collapse field value. Each sub-query independently collapses correctly via CollapsingPostFilter, but simpleCombine() merges results by Lucene doc ID only - it has no awareness of the collapse field. Different sub-queries may select different group heads for the same field value, and both survive the merge.

However it is well know limitation that :[ "In order to use these features with SolrCloud, the documents must be located on the same shard."|https://solr.apache.org/guide/solr/latest/query-guide/collapse-and-expand-results.html]

Solution

Removing collapsed duplicates by delegating to SolrIndexSearcher with the CollapsingPostFilter by forming the query using PrecomputedScoreQuery to preserve original scores with filter on the docSet from combined sub-queries. The duplicates are removed honouring the collapse query criteria.

Tests

Added comprehensive test with Collapse Query.

Checklist

Please review the following and check all that apply:

• I have reviewed the guidelines for How to Contribute and my code conforms to the standards described there to the best of my ability.
• I have created a Jira issue and added the issue ID to my pull request title.
• I have given Solr maintainers access to contribute to my PR branch. (optional but recommended, not available for branches on forks living under an organisation)
• I have developed this patch against the main branch.
• I have run ./gradlew check.
• I have added tests for my changes.
• I have added documentation for the Reference Guide
• I have added a changelog entry for my change