[Backport 2.x] Fix multi-search with template doesn't return status code (#16265)

[gaobinlong]

Description

Backport #16265 to 2.x.

Related Issues

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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[github-actions]

❌ Gradle check result for 4bc5a07: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[reta]

* What went wrong:
Execution failed for task ':modules:lang-mustache:spotlessJavaCheck'.
> The following files had format violations:
      src/main/java/org/opensearch/script/mustache/MultiSearchTemplateResponse.java
          @@ -32,8 +32,8 @@
           
           package·org.opensearch.script.mustache;
           
          +import·org.opensearch.ExceptionsHelper;
           import·org.opensearch.LegacyESVersion;
          -import·org.opensearch.ExceptionsHelper;
           import·org.opensearch.OpenSearchException;
           import·org.opensearch.action.search.MultiSearchResponse;
           import·org.opensearch.common.Nullable;
  Run './gradlew :modules:lang-mustache:spotlessApply' to fix these violations.

[github-actions]

✅ Gradle check result for 005338d: SUCCESS

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.79%. Comparing base (5947002) to head (005338d).
Report is 11 commits behind head on 2.x.

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x   #16312      +/-   ##
============================================
+ Coverage     71.74%   71.79%   +0.04%     
- Complexity    65022    65051      +29     
============================================
  Files          5302     5303       +1     
  Lines        303866   303858       -8     
  Branches      44192    44188       -4     
============================================
+ Hits         218012   218155     +143     
+ Misses        67648    67501     -147     
+ Partials      18206    18202       -4     

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