Enhance search preference based routing for WRR

[linuxpi]

Description

Various enhancements to search preference for Weighed Round Robin shard routing

Issues Resolved

• [Weighted Round Robin] Improve Weighted Round Robin shard rounting  #6857
• [Weighted Round Robin] Introduce a cluster setting to bypass Weighted Round Robin  #6858
• [Weighted Round Robin] Enable failopen for requests with only 1 shard in ShardIterator #6862

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)

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]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/12913/
• CommitID: 7473ec0
  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/12915/
• CommitID: d0ae3d8

[codecov-commenter]

Codecov Report

Merging #6834 (4be3054) into main (07565ad) will increase coverage by 0.01%.
The diff coverage is 53.84%.

📣 This organization is not using Codecov’s GitHub App Integration. We recommend you install it so Codecov can continue to function properly for your repositories. Learn more

@@             Coverage Diff              @@
##               main    #6834      +/-   ##
============================================
+ Coverage     70.65%   70.67%   +0.01%     
- Complexity    59162    59205      +43     
============================================
  Files          4812     4812              
  Lines        283615   283631      +16     
  Branches      40896    40898       +2     
============================================
+ Hits         200394   200443      +49     
+ Misses        66764    66728      -36     
- Partials      16457    16460       +3     

Impacted Files	Coverage Δ
...ensearch/cluster/routing/WeightedRoutingUtils.java	68.42% <0.00%> (-8.05%)	⬇️
...rg/opensearch/common/settings/ClusterSettings.java	92.50% <ø> (ø)
...g/opensearch/cluster/routing/OperationRouting.java	80.50% <50.00%> (-0.04%)	⬇️
...arch/cluster/routing/FailAwareWeightedRouting.java	74.41% <62.50%> (-1.90%)	⬇️
...search/cluster/routing/IndexShardRoutingTable.java	87.78% <100.00%> (+0.71%)	⬆️

... and 494 files with indirect coverage changes

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[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/12916/
• CommitID: 0c908db

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/12924/
• CommitID: 256ba08

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/12925/
• CommitID: dc9ab0d

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/12984/
• CommitID: 55ef13d
  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:

      1 org.opensearch.snapshots.DedicatedClusterSnapshotRestoreIT.testIndexDeletionDuringSnapshotCreationInQueue
      1 org.opensearch.indices.replication.SegmentReplicationRelocationIT.testRelocateWithQueuedOperationsDuringHandoff

• URL: https://build.ci.opensearch.org/job/gradle-check/12985/
• CommitID: dc9ab0d
  Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[gbbafna]

can we create an issue where we list out the problems which this PR is solving ?

[linuxpi]

can we create an issue where we list out the problems which this PR is solving ?

@gbbafna i've created issues corresponding to this PR and updated description

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=indices.shrink/30_copy_settings/Copy settings during shrink index}

• URL: https://build.ci.opensearch.org/job/gradle-check/13088/
• CommitID: 4be3054
  Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[Bukhtawar]

LGTM

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.cluster.allocation.AwarenessAllocationIT.testThreeZoneOneReplicaWithForceZoneValueAndLoadAwareness

• URL: https://build.ci.opensearch.org/job/gradle-check/13090/
• CommitID: 0f7e026
  Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[opensearch-trigger-bot]

The backport to 2.x failed:

The process '/usr/bin/git' failed with exit code 128

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/backport-2.x 2.x
# Navigate to the new working tree
pushd ../.worktrees/backport-2.x
# Create a new branch
git switch --create backport/backport-6834-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 d8d6e7324adb4be088cab8e1fa5833e18ef19109
# Push it to GitHub
git push --set-upstream origin backport/backport-6834-to-2.x
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-6834-to-2.x.