With only GlobalAggregation in request causes unnecessary wrapping with MultiCollector

[sohami]

Description

Avoid adding redundant multi collector wrapper when only global agg is present in the search request

Related Issues

Resolves #8097

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff
• Commit changes are listed out in CHANGELOG.md file (See: Changelog)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[sohami]

@reta Tagging you for the review

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.search.backpressure.SearchBackpressureIT.testSearchTaskCancellationWithHighCpu

• URL: https://build.ci.opensearch.org/job/gradle-check/17826/
• CommitID: a2ce220
  Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[codecov]

Codecov Report

Merging #8125 (28a9f20) into main (4228075) will decrease coverage by 0.07%.
The diff coverage is 88.88%.

@@             Coverage Diff              @@
##               main    #8125      +/-   ##
============================================
- Coverage     70.98%   70.92%   -0.07%     
+ Complexity    56714    56612     -102     
============================================
  Files          4722     4722              
  Lines        267608   267608              
  Branches      39216    39216              
============================================
- Hits         189962   189792     -170     
- Misses        61589    61789     +200     
+ Partials      16057    16027      -30     

Impacted Files	Coverage Δ
...n/java/org/opensearch/search/query/QueryPhase.java	78.80% <88.88%> (ø)

... and 456 files with indirect coverage changes

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.remotestore.SegmentReplicationUsingRemoteStoreIT.testPrimaryStopped_ReplicaPromoted

• URL: https://build.ci.opensearch.org/job/gradle-check/17827/
• CommitID: 28a9f20
  Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[reta]

@reta Tagging you for the review

Thanks @sohami !

[opensearch-trigger-bot]

The backport to 2.x failed:

The process '/usr/bin/git' failed with exit code 128

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/backport-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/backport-2.x
# Create a new branch
git switch --create backport/backport-8125-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 90678c2d76ed1c31aebc85a23fe5be12f6e81417
# Push it to GitHub
git push --set-upstream origin backport/backport-8125-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-8125-to-2.x.

[reta]

sorry, @sohami, 2.x needs manual backport ...

[sohami]

Will manually backport the changes

[sohami]

@reta Backport PR: #8129 Thanks for the review!