[Backport 2.x] Make verifier return type as ActionResponse

[opensearch-trigger-bot]

Backport 8386d10 from #7167.

[codecov-commenter]

Codecov Report

Merging #7342 (a50fece) into 2.x (ea11a60) will increase coverage by 0.02%.
The diff coverage is n/a.

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@@             Coverage Diff              @@
##                2.x    #7342      +/-   ##
============================================
+ Coverage     70.30%   70.33%   +0.02%     
+ Complexity    59731    59724       -7     
============================================
  Files          4850     4850              
  Lines        287193   287193              
  Branches      41727    41727              
============================================
+ Hits         201922   201986      +64     
+ Misses        68385    68357      -28     
+ Partials      16886    16850      -36     

Impacted Files	Coverage Δ
...a/org/opensearch/test/rest/RestActionTestCase.java	79.31% <ø> (ø)

... and 472 files with indirect coverage changes

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.search.SearchWeightedRoutingIT.testStrictWeightedRoutingWithCustomString
      1 org.opensearch.indices.replication.SegmentReplicationIT.testScrollCreatedOnReplica

• URL: https://build.ci.opensearch.org/job/gradle-check/14692/
• CommitID: a50fece
  Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.