[Backport 2.x] Make SearchTemplateRequest implement IndicesRequest.Replaceable

[opensearch-trigger-bot]

Backport c73f727 from #9122.

[opensearch-trigger-bot]

Compatibility status:

> Task :checkCompatibility
Incompatible components: [https://github.com/opensearch-project/geospatial.git, https://github.com/opensearch-project/alerting.git, https://github.com/opensearch-project/anomaly-detection.git, https://github.com/opensearch-project/k-nn.git, https://github.com/opensearch-project/performance-analyzer.git]
Components skipped due to git failures: [https://github.com/opensearch-project/opensearch-oci-object-storage.git]
Compatible components: [https://github.com/opensearch-project/security.git, https://github.com/opensearch-project/notifications.git, https://github.com/opensearch-project/neural-search.git, https://github.com/opensearch-project/index-management.git, https://github.com/opensearch-project/security-analytics.git, https://github.com/opensearch-project/sql.git, https://github.com/opensearch-project/job-scheduler.git, https://github.com/opensearch-project/observability.git, https://github.com/opensearch-project/asynchronous-search.git, https://github.com/opensearch-project/cross-cluster-replication.git, https://github.com/opensearch-project/common-utils.git, https://github.com/opensearch-project/reporting.git, https://github.com/opensearch-project/ml-commons.git, https://github.com/opensearch-project/performance-analyzer-rca.git]

BUILD SUCCESSFUL in 25m 16s

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      2 org.opensearch.remotestore.RemoteStoreIT.testRemoteTranslogCleanup
      1 org.opensearch.repositories.azure.AzureBlobContainerRetriesTests.testWriteLargeBlob
      1 org.opensearch.remotestore.multipart.RemoteStoreMultipartIT.testRemoteTranslogCleanup

• URL: https://build.ci.opensearch.org/job/gradle-check/22532/
• CommitID: b4e424c
  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 #9275 (b4e424c) into 2.x (bc69838) will decrease coverage by 0.16%.
Report is 2 commits behind head on 2.x.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##                2.x    #9275      +/-   ##
============================================
- Coverage     70.88%   70.72%   -0.16%     
+ Complexity    57490    57463      -27     
============================================
  Files          4758     4758              
  Lines        271801   271804       +3     
  Branches      40090    40090              
============================================
- Hits         192661   192236     -425     
- Misses        62624    63119     +495     
+ Partials      16516    16449      -67     

Files Changed	Coverage Δ
...nsearch/script/mustache/SearchTemplateRequest.java	78.18% <0.00%> (-2.20%)	⬇️

... and 454 files with indirect coverage changes