[Backport 2.x][Search Pipelines] Add default_search_pipeline index setting (#7470)

[msfroh]

• [Search Pipelines] Add default_search_pipeline index setting

Once users have defined and tested a search pipeline, they may want to apply it by default to all queries hitting a given index.

Users should be able to bypass the default pipeline for the index by explicitly specifying search_pipeline=_none in the URL parameter of their search request.

Signed-off-by: Michael Froh [email protected]

• Rename default search pipeline setting and add getter/setter

Also change version check for ad hoc pipeline to 2.8

Signed-off-by: Michael Froh [email protected]

• Add tests for new IndexSettings methods

Signed-off-by: Michael Froh [email protected]

• Update test to reflect change to FeatureFlagSetter

Signed-off-by: Michael Froh [email protected]

---

Signed-off-by: Michael Froh [email protected]
(cherry picked from commit 5984735)

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[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/15510/
• CommitID: d48d329
  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?

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/15532/
• CommitID: 5f55ba3

[codecov]

Codecov Report

Merging #7589 (b2e812c) into 2.x (1dbdf76) will decrease coverage by 0.13%.
The diff coverage is 91.30%.

@@             Coverage Diff              @@
##                2.x    #7589      +/-   ##
============================================
- Coverage     70.31%   70.19%   -0.13%     
+ Complexity    59937    59934       -3     
============================================
  Files          4882     4882              
  Lines        288376   288393      +17     
  Branches      41920    41924       +4     
============================================
- Hits         202777   202437     -340     
- Misses        68613    68968     +355     
- Partials      16986    16988       +2     

Impacted Files	Coverage Δ
...pensearch/common/settings/IndexScopedSettings.java	100.00% <ø> (ø)
...nsearch/search/pipeline/SearchPipelineService.java	82.81% <85.71%> (-0.34%)	⬇️
.../main/java/org/opensearch/index/IndexSettings.java	85.78% <100.00%> (+0.33%)	⬆️

... and 485 files with indirect coverage changes

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/15599/
• CommitID: 750cdfd
  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?

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      3 org.opensearch.search.SearchWeightedRoutingIT.testStrictWeightedRoutingWithCustomString

• URL: https://build.ci.opensearch.org/job/gradle-check/15600/
• CommitID: b2e812c
  Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.