NMS-17743: Add support for Elasticsearch 8.x

[Mohammad-Junid]

Adds support for Elasticsearch 8.15.2 version

JIRA: NMS-17743

Here some notable changes while migrating from ES7 to ES 8.15.2

• ES8 is supported JAVA 17 or later version see listed in the support matrix

Time API Changes

• ES7: Used Joda Time (org.joda.time.DateTime)
• ES8: Uses Java Time API (java.time)

Rounding Changes

• ES7: Used org.elasticsearch.common.rounding.Rounding
• ES8: Simplified to org.elasticsearch.common.Rounding

Reduce Operation Changes

• ES7: Used ReduceContext
• ES8: Uses AggregationReduceContext

Reduce Method Structure

• ES7: Direct reduce() implementation
• ES8: Uses AggregatorReducer pattern

Bucket Reduction Changes

• ES7: Used readList()/writeList()
• ES8: Uses readCollectionAsList()/writeCollection()

Order Stream Handling
ES7: Required additional boolean parameter
i.e

order = InternalOrder.Streams.readHistogramOrder(in, false);
InternalOrder.Streams.writeHistogramOrder(order, out, false);

ES8: Simplified signature

order = InternalOrder.Streams.readHistogramOrder(in);
InternalOrder.Streams.writeHistogramOrder(order, out);

Aggregation Execution Context

• ES7: Used LeafReaderContext directly

public LeafBucketCollector getLeafCollector(LeafReaderContext ctx, LeafBucketCollector sub)

• ES8: Uses AggregationExecutionContext wrapper
  public LeafBucketCollector getLeafCollector(AggregationExecutionContext ctx, LeafBucketCollector sub)

Sub-aggregation Building

• ES7: Used array of InternalAggregations
nternalAggregations[] subAggregationResults = buildSubAggsForBuckets(bucketOrdsToCollect);

• ES8: Uses IntFunction<InternalAggregations>
IntFunction<InternalAggregations> subAggregationResults = buildSubAggsForBuckets(bucketOrdsToCollect);

[cgorantla]

It would be good to know what has been updated in these files.

If you can add comments on the PR itself what are the changes needed for this to work will be helpful in reviewing this.

[mershad-manesh]

I have pushed changes to CircleCI config file on master branch, you might want to grab those changes