Change default search preference to _primary for searchable snapshot indices

[kotwanikunal]

Description

• Change the default search preference for searchable snapshot index queries to _primary which was added as a part of Add back primary shard preference for queries #7375
• The major driving factor for this change to maximize file cache efficiency for searchable snapshot indices which will prevent remote block fetches from repositories
• More details: [Searchable Snapshots / Segment Replication] Custom query routing for performance improvements #7436

Related Issues

Resolves #7593

• [Searchable Snapshots / Segment Replication] Custom query routing for performance improvements #7436
• Add back primary shard preference for queries #7375

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/15706/
• CommitID: 8263985
  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: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/15707/
• CommitID: 5758b30
  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?

[kotwanikunal]

Gradle Check (Jenkins) Run Completed with:

• RESULT: FAILURE ❌
• URL: https://build.ci.opensearch.org/job/gradle-check/15707/
• CommitID: 5758b30
  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?

org.opensearch.common.xcontent.XContentParserTests.testString

com.fasterxml.jackson.dataformat.yaml.JacksonYAMLParseException: The incoming YAML document exceeds the limit: 3145728 code points.
 at [Source: (byte[])"---
ow: "꠽꠾꠲꠱꠺꠸꠸꠼꠽꠽꠰꠲꠶꠱꠷꠴꠶꠽꠳꠸꠵꠴꠸꠻꠱꠸꠾꠽꠸꠶꠼꠰꠿꠱꠷꠵꠾꠲꠴꠱꠶꠰꠽꠻꠳꠱꠴꠳꠻꠰꠸꠺꠼꠳꠳꠳꠿꠻꠶꠾꠲꠺꠽꠺꠶꠽꠱꠿꠻꠿꠸꠴꠲꠶꠼꠵꠲\
  ꠿꠽꠵꠴꠺꠺꠳꠿꠹꠷꠲꠴꠿꠾꠿꠾꠷꠼꠷꠼꠸꠲꠶꠶꠶꠼꠴꠺꠱꠾꠴꠶꠰꠾꠾꠰꠱꠴꠼꠽꠿꠰꠳꠺꠰꠰꠺꠽꠼꠱꠰꠿꠵꠲꠱꠰꠼꠽꠽꠵꠽꠴꠼꠳꠴꠱꠱꠺꠺꠵꠷꠱꠰꠶꠷꠾꠺꠴꠸꠷\
  ꠷꠵꠵꠺"[truncated 9168338 bytes]; line: 37579, column: 20]

[kotwanikunal]

Looks related to #7615 and unrelated to the changes in this PR.

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/15711/
• CommitID: 5758b30

[codecov]

Codecov Report

Merging #7628 (1a366c2) into main (eb51f2b) will increase coverage by 0.07%.
The diff coverage is 80.00%.

@@             Coverage Diff              @@
##               main    #7628      +/-   ##
============================================
+ Coverage     70.72%   70.79%   +0.07%     
- Complexity    56044    56122      +78     
============================================
  Files          4676     4676              
  Lines        265969   265974       +5     
  Branches      39061    39063       +2     
============================================
+ Hits         188102   188301     +199     
+ Misses        61902    61746     -156     
+ Partials      15965    15927      -38     

Impacted Files	Coverage Δ
...g/opensearch/cluster/routing/OperationRouting.java	80.35% <80.00%> (-0.02%)	⬇️

... and 447 files with indirect coverage changes

[reta]

Looks related to #7615 and unrelated to the changes in this PR.

Should be fixed, sorry about that @kotwanikunal

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/15978/
• CommitID: 1a366c2

[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-7628-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 fa878ae05ea2016bee99a8fc305ae506050f65d4
# Push it to GitHub
git push --set-upstream origin backport/backport-7628-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-7628-to-2.x.