With only GlobalAggregation in request causes unnecessary wrapping with MultiCollector

[sohami]

Description

Backport of #8125

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[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.snapshots.DedicatedClusterSnapshotRestoreIT.testIndexDeletionDuringSnapshotCreationInQueue
      1 org.opensearch.remotestore.SegmentReplicationUsingRemoteStoreIT.testPressureServiceStats
      1 org.opensearch.remotestore.RemoteStoreRefreshListenerIT.testRemoteRefreshRetryOnFailure

• URL: https://build.ci.opensearch.org/job/gradle-check/17835/
• CommitID: 9916712
  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 #8129 (9916712) into 2.x (4a090af) will decrease coverage by 0.01%.
The diff coverage is 88.88%.

@@             Coverage Diff              @@
##                2.x    #8129      +/-   ##
============================================
- Coverage     70.71%   70.71%   -0.01%     
+ Complexity    56848    56841       -7     
============================================
  Files          4703     4703              
  Lines        269056   269056              
  Branches      39770    39770              
============================================
- Hits         190263   190255       -8     
- Misses        62452    62507      +55     
+ Partials      16341    16294      -47     

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

... and 466 files with indirect coverage changes