[Backport 2.x] Fix some test methods in SimulatePipelineRequestParsingTests never run and fix test failure

[gaobinlong]

Description

Backport #10496 to 2.x branch.

Related Issues

#10493

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)
• Public documentation issue/PR created

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.

[github-actions]

Compatibility status:

Checks if related components are compatible with change d9e0ad0

Incompatible components

Skipped components

Compatible components

Compatible components: [https://github.com/opensearch-project/security.git, https://github.com/opensearch-project/alerting.git, https://github.com/opensearch-project/index-management.git, https://github.com/opensearch-project/anomaly-detection.git, https://github.com/opensearch-project/asynchronous-search.git, https://github.com/opensearch-project/sql.git, https://github.com/opensearch-project/common-utils.git, https://github.com/opensearch-project/observability.git, https://github.com/opensearch-project/job-scheduler.git, https://github.com/opensearch-project/reporting.git, https://github.com/opensearch-project/cross-cluster-replication.git, https://github.com/opensearch-project/k-nn.git, https://github.com/opensearch-project/security-analytics.git, https://github.com/opensearch-project/custom-codecs.git, https://github.com/opensearch-project/geospatial.git, https://github.com/opensearch-project/ml-commons.git, https://github.com/opensearch-project/performance-analyzer.git, https://github.com/opensearch-project/performance-analyzer-rca.git, https://github.com/opensearch-project/notifications.git, https://github.com/opensearch-project/neural-search.git]

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/27917/
• CommitID: d9e0ad0

[codecov]

Codecov Report

Merging #10631 (d9e0ad0) into 2.x (eadbef5) will increase coverage by 0.10%.
Report is 1 commits behind head on 2.x.
The diff coverage is n/a.

@@             Coverage Diff              @@
##                2.x   #10631      +/-   ##
============================================
+ Coverage     70.81%   70.92%   +0.10%     
- Complexity    58473    58560      +87     
============================================
  Files          4830     4830              
  Lines        276440   276440              
  Branches      40586    40586              
============================================
+ Hits         195766   196063     +297     
+ Misses        64001    63609     -392     
- Partials      16673    16768      +95     

see 455 files with indirect coverage changes

[gaobinlong]

Change log is not needed for this test related PR, and all other tests have passed yet, @dblock , please help to review this backport PR, thanks!

[dblock]

We can skip changelog for this, nbd.